Filed pursuant to Rule 424(b)(2)
Registration Statement No. 333-223921

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities to be Registered	Proposed Maximum   Aggregate Offering     Price	Amount of  Registration Fee(1)(2)
Common Stock, par value $0.01 per share	$750,000,000	$93,375

(1) Calculated in accordance with Rules 457(o) and 457(r) under the Securities Act of 1933, as amended (“Securities Act”). This “Calculation of Registration Fee” table shall be deemed to update the “Calculation of Registration Fee” table in the registrant’s Registration Statement on Form S-3 (File No. 333-223921) (“New Registration Statement”).

(2) Pursuant to Rules 456(b) and 457(p) under the Securities Act, $17,450 of registration fee that was previously paid in respect of shares of common stock, $0.01 par value per share, of the registrant with a proposed maximum aggregate offering price of $150,236,808 that were previously registered but remained unsold pursuant to the registrant’s prior Registration Statement on Form S-3 (File No. 333-203074) filed March 27, 2015 (“Prior Registration Statement”) are being carried forward and have been applied against the registration fee for this offering. Accordingly, a registration fee in the amount of $75,925 has been paid with respect to this offering. Under Rule 416(a)(6) under the Securities Act, the Prior Registration Statement was deemed terminated effective as of the date of effectiveness of the New Registration Statement.

Prospectus Supplement

(To Prospectus dated March 26, 2018)

$750,000,000

Crown Castle International Corp.

Common Stock

On April 6, 2018, we entered into sales agreements with each of Merrill Lynch, Pierce, Fenner & Smith Incorporated, Barclays Capital Inc., Citigroup Global Markets Inc., Credit Agricole Securities (USA) Inc., Fifth Third Securities, Inc., Jefferies LLC, J.P. Morgan Securities LLC, Mizuho Securities USA LLC, Morgan Stanley & Co. LLC, MUFG Securities Americas Inc., RBC Capital Markets, LLC, SG Americas Securities, LLC, SMBC Nikko Securities America, Inc., SunTrust Robinson Humphrey, Inc., TD Securities (USA) LLC and Wells Fargo Securities, LLC (each, a “Sales Agent” and collectively, “Sales Agents”), relating to the offering of shares of our common stock, par value $0.01 per share, having an aggregate gross sales price up to $750,000,000, to be made by this prospectus supplement and the accompanying prospectus.

In accordance with the terms of the sales agreements, sales of shares of our common stock under this prospectus supplement and the accompanying prospectus, if any, will be made by means of ordinary brokers’ transactions on the New York Stock Exchange (“NYSE”) or otherwise at market prices prevailing at the time of sale, at prices related to prevailing market prices or, subject to our specific instructions, at negotiated prices.

Under the terms of the sales agreements, we also may sell shares of our common stock to any Sales Agent as principal for its own account. If we sell shares to any Sales Agent as principal, we will enter into a separate terms agreement setting forth the terms of such transaction, and we will describe the agreement in a separate prospectus supplement or pricing supplement.

No Sales Agent is required to sell any specific number or dollar amount of shares of our common stock, but, subject to the terms and conditions of the sales agreements, each Sales Agent has agreed to use its commercially reasonable efforts to sell the shares offered as our agent. There is no arrangement for shares to be received in an escrow, trust or similar arrangement. The offering of shares of common stock pursuant to the sales agreements will terminate upon the earlier of (i) the issuance and sale of shares of our common stock subject to the sales agreements having an aggregate gross sales price of $750,000,000 and (ii) with respect to a particular sales agreement, the termination of such sales agreement by us or by the applicable Sales Agent as permitted therein.

The compensation to each Sales Agent for sales of our common stock will be a commission that will not exceed, but may be lower than, 2.00% of the gross sales price of the shares sold through it as agent pursuant to the applicable sales agreement. We intend to use the net proceeds from any sales under this prospectus supplement for general corporate purposes, which may include (i) the funding of future acquisitions or investments or (ii) the repayment or repurchase of any outstanding indebtedness.

Our common stock is listed on the NYSE under the symbol “CCI.” On April 5, 2018, the last reported sales price of our common stock as reported on the NYSE was $109.80 per share.

Investing in our common stock involves risk. See “Risk Factors” beginning on page S-3 of this prospectus supplement, page 3 of the accompanying prospectus and page 9 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2017, as updated by reports and documents we file with the Securities and Exchange Commission that are incorporated by reference herein.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

BofA Merrill Lynch	Barclays	Citigroup	Credit Agricole CIB
Fifth Third Securities	Jefferies	J.P. Morgan	Mizuho Securities
Morgan Stanley	MUFG	RBC Capital Markets	SOCIETE GENERALE
SMBC Nikko	SunTrust Robinson Humphrey	TD Securities	Wells Fargo Securities

Prospectus Supplement dated April 6, 2018

TABLE OF CONTENTS

Prospectus Supplement

	Page
ABOUT THIS PROSPECTUS SUPPLEMENT		iii
CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS		iii
PROSPECTUS SUPPLEMENT SUMMARY		S-1
THE OFFERING		S-2
RISK FACTORS		S-3
USE OF PROCEEDS		S-6
CAPITALIZATION		S-7
PRICE RANGE OF COMMON STOCK AND DIVIDEND POLICY		S-9
DESCRIPTION OF CAPITAL STOCK		S-10
MATERIAL UNITED STATES FEDERAL INCOME  TAX CONSIDERATIONS		S-13
PLAN OF DISTRIBUTION		S-31
LEGAL MATTERS		S-33
EXPERTS		S-33
WHERE YOU CAN FIND MORE INFORMATION		S-34
Prospectus
ABOUT THIS PROSPECTUS		1
THE COMPANY		2
RISK FACTORS		3
CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS		4
SELLING SECURITY HOLDERS		5
USE OF PROCEEDS		6
RATIO OF EARNINGS TO FIXED CHARGES AND EARNINGS TO COMBINED FIXED CHARGES AND DIVIDENDS ON PREFERRED STOCK AND LOSSES ON PURCHASES OF PREFERRED STOCK		7
DESCRIPTION OF DEBT SECURITIES		8
DESCRIPTION OF CAPITAL STOCK		20
DESCRIPTION OF WARRANTS		28
PLAN OF DISTRIBUTION		29
LEGAL MATTERS		31
EXPERTS		32
WHERE YOU CAN FIND MORE INFORMATION		32

i

You should rely only on the information contained in or incorporated by reference in this prospectus supplement and the accompanying prospectus or any free writing prospectus prepared by us or on our behalf. We have not, and the Sales Agents have not, authorized anyone to provide you with additional or different information. We are not, and the Sales Agents are not, making an offer to sell these securities in any jurisdiction where such offer or sale is not permitted. You should assume that the information contained in this prospectus supplement, the accompanying prospectus or any free writing prospectus prepared by us or on our behalf is accurate only as of the date of such document, as applicable, and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference. Our business, financial condition, results of operations and prospects may have changed since these dates.

ii

ABOUT THIS PROSPECTUS SUPPLEMENT

Unless otherwise indicated or the context otherwise requires, the terms “Crown Castle,” “we,” “our,” “the Company” and “us” refer to Crown Castle International Corp., a Delaware corporation, and its subsidiaries on a consolidated basis. As used herein, the term “including,” and any variation thereof, means “including without limitation.” Unless the context otherwise requires, the use of the word “or” herein is not exclusive.

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering and certain other matters. The second part, the accompanying prospectus, gives more general information about us and our debt securities and capital stock. Generally, when we refer to “this prospectus,” we are referring to both parts of this document combined. To the extent information in this prospectus supplement conflicts with information in the accompanying prospectus, you should rely on the information in this prospectus supplement.

CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS

The statements contained in or incorporated by reference in this prospectus supplement include certain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, with respect to the financial condition, results of operations, business strategies, operating efficiencies or synergies, competitive positions, growth opportunities for existing products, plans and objectives of management, markets for our stock and other matters that are based on our management’s expectations as of the filing date of this prospectus supplement with the Securities and Exchange Commission (“SEC”). Statements contained in or incorporated by reference in this prospectus supplement that are not historical facts are hereby identified as “forward-looking statements” for the purpose of the safe harbor provided by Section 21E of the Securities Exchange Act of 1934, as amended (“Exchange Act”), and Section 27A of the Securities Act of 1933, as amended (“Securities Act”). In addition, words such as “estimate,” “anticipate,” “project,” “plan,” “intend,” “believe,” “expect,” “likely,” “predicted,” “positioned” and any variations of these words and similar expressions are intended to identify forward-looking statements. These forward-looking statements include plans, projections and estimates and are found at various places throughout this prospectus supplement and the documents incorporated by reference herein. Such forward-looking statements include (1) expectations regarding anticipated growth in the wireless industry, carriers’ investments in their networks, tenant additions, customer consolidation or ownership changes, and demand for our communications infrastructure (as defined below), (2) expectations regarding non-renewals of tenant contracts, (3) availability and adequacy of cash flows and liquidity for, or plans regarding, future discretionary investments, including capital expenditures, (4) potential benefits of our discretionary investments, including acquisitions, (5) anticipated growth in our financial results, including future revenues, Adjusted EBITDA, segment site rental gross margin, segment network services and other gross margin, segment operating profit and operating cash flows, (6) expectations regarding our capital structure and the credit markets, our availability and cost of capital, and our ability to service our debt and comply with debt covenants and the plans for and the benefits of any future refinancings, (7) expectations related to remaining qualified as a real estate investment trust (“REIT”) and the advantages, benefits or impact of, or opportunities created by, our REIT status and the impact of the Tax Cuts and Jobs Act (“Tax Reform Act”), (8) the realization and utilization of our net operating loss carryforwards (“NOLs”), (9) our dividend policy and the timing, amount, growth or tax characterization of any dividends and (10) expectations regarding the use of net proceeds from this offering.

These forward-looking statements should, therefore, be considered in light of various risks, uncertainties and assumptions, including prevailing market conditions and other important factors, including those set forth in or incorporated by reference in this prospectus supplement. Important factors that could cause actual results to differ materially from estimates or projections contained in the forward-looking statements include those factors described in the sections entitled “Risk Factors” beginning on page S-3 of this prospectus supplement, page 3 of the accompanying prospectus and page 9 of our Annual Report on Form 10-K for the fiscal year ended

iii

December 31, 2017, as updated by annual, quarterly and other reports and documents we file with the SEC that are incorporated by reference herein. Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those expected. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this prospectus supplement or the date of the other documents incorporated by reference herein. You also should understand that it is not possible to predict or identify all such factors and that the risk factors as listed in our filings with the SEC should not be considered a complete statement of all potential risks and uncertainties.

iv

PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights information from this prospectus supplement and may not contain all the information that may be important to you. Accordingly, you should read this entire prospectus supplement, the accompanying prospectus, any free writing prospectus prepared by us or on our behalf that we may provide to you in connection with this offering and the documents incorporated and deemed to be incorporated by reference herein and therein, including the financial data and related notes, before making an investment decision. You may obtain a copy of the documents incorporated by reference by following the instructions in the section titled “Where You Can Find More Information” in this prospectus supplement. You should pay special attention to the “Risk Factors” sections of this prospectus supplement, the accompanying prospectus and our Annual Report on Form 10-K for the fiscal year ended December 31, 2017, as updated by annual, quarterly and other reports and documents we file with the SEC that are incorporated by reference in this prospectus supplement and the accompanying prospectus, to determine whether an investment in our common stock is appropriate for you.

The Business

We own, operate and lease shared communications infrastructure that is geographically dispersed throughout the U.S. and Puerto Rico, including, as of December 31, 2017, (1) approximately 40,000 towers and other structures, such as rooftops (collectively, “towers”), and (2) approximately 60,000 route miles of fiber primarily supporting small cell networks (“small cells”) and fiber solutions. Our towers, fiber and small cells assets are collectively referred to herein as “communications infrastructure,” and our customers on our communications infrastructure are referred to herein as “tenants.” Our customers include AT&T, T-Mobile, Verizon Wireless and Sprint, which collectively accounted for 83% of our site rental revenues for the year ended December 31, 2017.

Our core business is providing access, including space or capacity, to our shared communications infrastructure via long-term contracts in various forms, including lease, license, sublease and service agreements. We seek to increase our site rental revenues by adding more tenants on our shared communications infrastructure, which we expect to result in significant incremental cash flows due to our low incremental operating costs. Site rental revenues represented 84% of our consolidated net revenues for the year ended December 31, 2017.

As of December 31, 2017, approximately 56% and 71% of our towers are located in the 50 and 100 largest U.S. basic trading areas (“BTAs”), respectively. Our towers have a significant presence in each of the top 100 BTAs. As of December 31, 2017, we derive in excess of one-third of our Towers segment site rental gross margin on land and other property interests (collectively, “land”) that we own, including fee interests and perpetual easements, and we derive approximately two-thirds of our Towers segment site rental gross margin from land that we lease, sublease, manage or license.

The majority of our small cells and fiber are located in major metropolitan areas, including a presence within every major U.S. market. The vast majority of our fiber assets are located on public rights-of-way.

As part of our effort to provide comprehensive communications infrastructure solutions, we also offer certain network services primarily relating to our towers and small cells, predominately consisting of (1) site development services relating to existing or new tenant equipment installations, including: site acquisition, architectural and engineering, or zoning and permitting and (2) tenant equipment installation or subsequent augmentations. The large majority of our network services and other revenues relate to our Towers segment.

Our principal executive offices are located at 1220 Augusta Drive, Suite 600, Houston, Texas 77057, and our telephone number is (713) 570-3000. We maintain a website at www.crowncastle.com. Except as expressly stated herein, no information contained in, or that can be accessed through, our website is incorporated by reference into this prospectus supplement or the accompanying prospectus, and no such information should be considered a part of this prospectus supplement or the accompanying prospectus.

S-1

THE OFFERING

The summary below contains basic information about this offering and may not contain all of the information that may be important to you. You should read this entire prospectus supplement, the accompanying prospectus, any free writing prospectus prepared by us or on our behalf that we may provide to you in connection with this offering and the documents incorporated and deemed to be incorporated by reference herein and therein before making an investment decision. As used in this section, “we,” “our” and “us” refer only to Crown Castle International Corp. and not to its consolidated subsidiaries.

Issuer Crown Castle International Corp., a Delaware corporation.

Common Stock Offered Shares of common stock with an aggregate gross sales price of up to $750,000,000.

NYSE Symbol for Common Stock CCI.

Use of Proceeds We intend to use the net proceeds from any sales under this prospectus supplement for general corporate purposes, which may include (i) the funding of future acquisitions or investments or (ii) the repayment or repurchase of any outstanding indebtedness. See “Use of Proceeds.”

Transfer Agent and Registrar Computershare Inc. is the transfer agent and registrar for our common stock.

Risk Factors

See the “Risk Factors” sections beginning on page S-3 of this prospectus supplement, page 3 of the accompanying prospectus and page 9 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2017, as updated by annual, quarterly and other reports and documents we file with the SEC that are incorporated by reference herein, for a discussion of factors to which you should refer and carefully consider prior to making an investment in our common stock.

S-2

RISK FACTORS

Investing in our common stock involves risks. Before purchasing any shares of our common stock, you should carefully consider the specific factors discussed below, together with all the other information contained in this prospectus supplement, the accompanying prospectus, any free writing prospectus prepared by us or on our behalf that we may provide to you in connection with this offering and the documents incorporated and deemed to be incorporated by reference herein and therein. For a further discussion of the risks, uncertainties and assumptions relating to our business, please see the discussion under the caption “Risk Factors” included in our Annual Report on Form 10-K for the year ended December 31, 2017, as updated by our annual, quarterly and other reports and documents we file with the SEC that are incorporated by reference in this prospectus supplement and the accompanying prospectus. The risks described below are not the only risks that we face. Additional risks and uncertainties not currently known to us or that we currently deem immaterial may also impair our business operations. Any of these risks may have a material adverse effect on our business, financial condition, results of operations and cash flows. In such a case, you may lose all or part of your investment in our common stock.

Risks Relating to Our Business

The risks, uncertainties and assumptions associated with our business include:

• Our business depends on the demand for our communications infrastructure, driven primarily by demand for data, and we may be adversely affected by any slowdown in such demand. Additionally, a reduction in the amount or change in the mix of network investment by our customers may materially and adversely affect our business (including reducing demand for tenant additions or network services).

• A substantial portion of our revenues is derived from a small number of customers, and the loss, consolidation or financial instability of any of such customers may materially decrease revenues or reduce demand for our communications infrastructure and network services.

• The expansion or development of our business, including through acquisitions, increased product offerings or other strategic growth opportunities, may cause disruptions in our business, which may have an adverse effect on our business, operations or financial results. Additionally, we may fail to realize all of the anticipated benefits of our November 2017 acquisition of LTS Group Holdings LLC, or those benefits may take longer to realize than expected.

• Our Fiber segment has expanded rapidly, and the Fiber business model contains certain differences from our Towers business model, resulting in different operational risks. If we do not successfully operate our Fiber business model or identify or manage the related operational risks, such operations may produce results that are less than anticipated.

• Failure to timely and efficiently execute on our construction projects could adversely affect our business.

• Our substantial level of indebtedness could adversely affect our ability to react to changes in our business, and the terms of our debt instruments and the terms of our 6.875% Mandatory Convertible Preferred Stock, Series A, par value $0.01 per share (“Mandatory Convertible Preferred Stock”) limit our ability to take a number of actions that our management might otherwise believe to be in our best interests. In addition, if we fail to comply with our covenants, our debt could be accelerated.

• We have a substantial amount of indebtedness. In the event we do not repay or refinance such indebtedness, we could face substantial liquidity issues and might be required to issue equity securities or securities convertible into equity securities, or sell some of our assets to meet our debt payment obligations.

• As a result of competition in our industry, we may find it more difficult to negotiate favorable rates on our new or renewing customer contracts.

• New technologies may significantly reduce demand for our communications infrastructure or negatively impact our revenues.

S-3

• If we fail to retain rights to our communications infrastructure, including the land interests under our towers and the right-of-way and other agreements related to our small cells and fiber solutions, our business may be adversely affected.

• Our network services business has historically experienced significant volatility in demand, which reduces the predictability of our results.

• New wireless technologies may not deploy or be adopted by customers as rapidly or in the manner projected.

• If we fail to comply with laws or regulations which regulate our business and which may change at any time, we may be fined or even lose our right to conduct some of our business.

• If radio frequency emissions from wireless handsets or equipment on our communications infrastructure are demonstrated to cause negative health effects, potential future claims could adversely affect our operations, costs or revenues.

• Certain provisions of our Restated Certificate of Incorporation (as defined below), By-laws (as defined below) and operative agreements, and domestic and international competition laws may make it more difficult for a third party to acquire control of us or for us to acquire control of a third party, even if such a change in control would be beneficial to our stockholders.

• We may be vulnerable to security breaches that could adversely affect our operations, business and reputation.

Risks Relating to Our REIT Status

The risks, uncertainties and assumptions associated with our REIT status include:

• Future dividend payments to our stockholders will reduce the availability of our cash on hand available to fund future discretionary investments, and may result in a need to incur indebtedness or issue equity securities to fund growth opportunities. In such event, the then-current economic, credit market or equity market conditions will impact the availability or cost of such financing, which may hinder our ability to grow our per share results of operations.

• Remaining qualified to be taxed as a REIT involves highly technical and complex provisions of the U.S. Internal Revenue Code of 1986, as amended (“Code”). Failure to remain qualified as a REIT would result in our inability to deduct dividends to stockholders when computing our taxable income, which would reduce our available cash.

• If we fail to pay scheduled dividends on our Mandatory Convertible Preferred Stock, in cash, common stock, or any combination of cash and common stock, we will be prohibited from paying dividends on our common stock, which may jeopardize our status as a REIT.

• Complying with REIT requirements, including the 90% distribution requirement, may limit our flexibility or cause us to forgo otherwise attractive opportunities, including certain discretionary investments and potential financing alternatives.

• REIT related ownership limitations and transfer restrictions may prevent or restrict certain transfers of our capital stock.

The present U.S. federal income tax treatment of REITs is subject to change, possibly with retroactive effect, by legislative, judicial or administrative action at any time, and any such change might adversely affect our REIT status or benefits or our business.

S-4

Risks Relating to Ownership of Our Common Stock

The price of our common stock may be volatile.

The market price of our common stock may be influenced by many factors, some of which are beyond our control, including those described in this “Risk Factors” section and the following:

• actual or anticipated fluctuations in our operating results or those of our competitors;

• announcements by us or our competitors of new products, significant contracts, acquisitions or strategic investments;

• our growth rate and the growth rates of our competitors;

• the financial market and general economic conditions;

• changes in stock market analyst recommendations regarding us, our competitors or the communications industry generally, or lack of analyst coverage of our common stock;

• sales of our common stock by our executive officers, directors and significant stockholders or sales of substantial amounts of our common stock;

• changes in accounting principles; and

• changes in tax laws and regulations.

In addition, fluctuations in yield rates in particular may give rise to arbitrage opportunities based upon changes in the relative values of our Mandatory Convertible Preferred Stock and our common stock. Any such arbitrage could, in turn, affect the market prices of our common stock and our Mandatory Convertible Preferred Stock.

Sales or issuances of substantial amounts of our common stock in the public market, or the perception that these sales or issuances may occur, or the conversion of our Mandatory Convertible Preferred Stock or the payment of dividends on the Mandatory Convertible Preferred Stock in the form of shares of our common stock, could cause the market price of our common stock to decline.

Sales or issuances of substantial amounts of our common stock in the public market, including pursuant to this offering, or the perception that these sales or issuances may occur, or the conversion of our Mandatory Convertible Preferred Stock or the payment of dividends on the Mandatory Convertible Preferred Stock in the form of shares of our common stock, or the perception that such conversions or dividends could occur, could cause the market price of our common stock to decline. This could also impair our ability to raise additional capital through the sale of our equity securities. Future sales or issuances of our common stock or other equity-related securities could be dilutive to holders of our common stock, including purchasers of our common stock in this offering.

Our common stock ranks junior to the Mandatory Convertible Preferred Stock with respect to dividends and amounts payable in the event of our liquidation.

Our common stock ranks junior to the Mandatory Convertible Preferred Stock with respect to the payment of dividends and amounts payable in the event of our liquidation, dissolution or winding-up. This means that, unless accumulated dividends have been paid or set aside for payment on all outstanding Mandatory Convertible Preferred Stock for all past completed dividend periods, no dividends may be declared or paid on our common stock. Likewise, in the event of our voluntary or involuntary liquidation, dissolution or winding-up, no distribution of our assets may be made to holders of our common stock until we have paid to holders of the Mandatory Convertible Preferred Stock a liquidation preference equal to $1,000.00 per share plus accrued and unpaid dividends.

For additional and more detailed information, please see “Description of Capital Stock” and the description of our capital stock set forth in the Capital Stock Description (as defined in “Where You Can Find More Information”) and incorporated by reference herein.

S-5

USE OF PROCEEDS

We intend to use the net proceeds from any sales under this prospectus supplement for general corporate purposes, which may include (i) the funding of future acquisitions or investments or (ii) the repayment or repurchase of any outstanding indebtedness.

S-6

CAPITALIZATION

The following table sets forth our cash and cash equivalents and capitalization as of December 31, 2017:

• on an actual basis; and

• on an as adjusted basis after giving effect to (i) the offering on January 16, 2018 of $750 million aggregate principal amount of 3.150% senior notes due 2023 and $1 billion aggregate principal amount of 3.800% senior notes due 2028 (collectively, “January 2018 Senior Notes Offering”) and the application of net proceeds therefrom and (ii) the offering on March 5, 2018 of 7,765,000 shares of our common stock (“March 2018 Equity Offering”) and the application of a portion of the net proceeds therefrom to repay outstanding borrowings under the Revolver (as defined below).

The following table does not reflect our receipt of any cash proceeds from the shares of our common stock offered hereby. The following data are qualified in their entirety by our financial statements and other information incorporated by reference herein. You should read this table in conjunction with “Risk Factors” and “Use of Proceeds.”

	Actual(6)		As Adjusted(6)
	(audited)		(unaudited)
	(dollars in thousands)
Cash and Cash Equivalents(1)(8)	$	314,094	$	591,298
Long-Term Debt:
Credit Facility:
Term Loan A Facility (maturing in August 2022)	$	2,396,588	$	2,396,588
Revolver (maturing in August 2022)(2)(7)(9)		980,000		—
Senior Secured Notes, Series 2009-1(3)(4)		101,313		101,313
January 2010 Senior Secured Tower Revenue Notes(7)		1,246,106		—
August 2010 Senior Secured Tower Revenue Notes(5)		995,354		995,354
2015 Senior Secured Tower Revenue Notes(5)		989,536		989,536
3.400% Senior Notes due 2021		849,859		849,859
2.250% Senior Notes due 2021		695,383		695,383
4.875% Senior Notes due 2022		842,090		842,090
5.250% Senior Notes due 2023		1,639,207		1,639,207
3.150% Senior Notes due 2023		—		741,769
3.849% Senior Secured Notes due 2023		992,663		992,663
3.200% Senior Notes due 2024		741,859		741,859
4.450% Senior Notes due 2026		891,145		891,145
3.700% Senior Notes due 2026		742,727		742,727
4.000% Senior Notes due 2027		493,833		493,833
3.650% Senior Notes due 2027		990,965		990,965
3.800% Senior Notes due 2028		—		988,451
4.750% Senior Notes due 2047		343,209		343,209
Capital Leases and Other Obligations		227,783		227,783
Total Debt	$	16,159,620	$	15,663,734
Less Current Maturities and Short-Term Debt	$	115,251	$	115,251
Total Long-Term Debt	$	16,044,369	$	15,548,483
Total Crown Castle International Corp. Stockholders’ Equity	$	12,339,082	$	13,107,250
Total Capitalization	$	28,498,702	$	28,770,984

(1) Exclusive of restricted cash.

S-7

(2) As of April 4, 2018, we had approximately $100 million of outstanding indebtedness under our $3.5 billion senior unsecured revolving credit facility (“Revolver”) and approximately $3.4 billion of unused borrowing availability under the Revolver.

(3) Includes Senior Secured Notes, Series 2009-1, Class A-1 and Senior Secured Notes, Series 2009-1, Class A-2.

(4) Excludes Senior Secured Notes, Series 2009-1, Class A-2 that have been repurchased by the Company. As of December 31, 2017, we had repurchased and held approximately $5 million of Senior Secured Notes, Series 2009-1, Class A-2.

(5) If the August 2010 Senior Secured Tower Revenue Notes and the Series 2015-1 and Series 2015-2 Senior Secured Tower Revenue Notes (together, “Senior Secured Tower Revenue Notes”) are not repaid in full by their respective anticipated repayment dates in 2020, 2022 and 2025, as applicable, then substantially all of the cash flows of the issuers of such Senior Secured Tower Revenue Notes must be applied to make principal payments on the applicable series and class of Senior Secured Tower Revenue Notes thereafter. In addition, if the Senior Secured Tower Revenue Notes are not repaid in full by their respective anticipated repayment dates, then the interest rates on the applicable series and class of such Senior Secured Tower Revenue Notes will increase by the greater of (i) 5% per annum over their current rates or (ii) the amount, if any, by which the sum of the following exceeds the note rate for a class of Senior Secured Tower Revenue Notes: the yield to maturity on the applicable anticipated repayment date of the United States treasury security having a term closest to 10 years, plus 5%, plus the post-anticipated repayment date spread for such class of Senior Secured Tower Revenue Notes.

(6) Balances reflect debt issuance costs as a direct reduction from the respective carrying amounts of debt, except debt issuance costs associated with the Revolver.

(7) The proceeds from the January 2018 Senior Notes Offering were used to repay (1) in full the January 2010 Senior Secured Tower Revenue Notes, issued by certain of our subsidiaries and (2) a portion of the outstanding borrowings under the Revolver. The as adjusted Revolver balance excludes normal Revolver activities in the ordinary course of business after December 31, 2017.

(8) The as adjusted Cash and Cash Equivalents balance reflects an increase equal to the approximately $275 million remaining net proceeds from the March 2018 Equity Offering that were not applied towards reducing the outstanding indebtedness under the Revolver.

(9) The as adjusted Revolver balance reflects the application of approximately $565 million of the net proceeds from the March 2018 Equity Offering to reduce the outstanding indebtedness under the Revolver.

S-8

PRICE RANGE OF COMMON STOCK AND DIVIDEND POLICY

Our common stock trades on the NYSE under the symbol “CCI.” The following table sets forth, for the periods indicated, the high and low sale prices per share of common stock as reported on the NYSE and the declared dividends per share.

	High		Low		Quarterly Cash Dividend Per Share of Common Stock
Fiscal year ended December 31, 2016
First quarter	$	88.46	$	75.71	$	0.885
Second quarter	$	101.44	$	85.59	$	0.885
Third quarter	$	102.82	$	89.82	$	0.885
Fourth quarter	$	95.84	$	79.38	$	0.95
Fiscal year ended December 31, 2017
First quarter	$	95.45	$	83.96	$	0.95
Second quarter	$	104.68	$	93.22	$	0.95
Third quarter	$	108.88	$	93.14	$	0.95
Fourth quarter	$	114.97	$	99.33	$	1.05
Fiscal year ending December 31, 2018
First quarter	$	114.47	$	100.76	$	1.05
Second quarter (through April 5, 2018)	$	110.44	$	106.47	$	—

On April 5, 2018, the last reported sale price of our common stock on the NYSE was $109.80 per share. As of April 4, 2018, there were 414,822,516 shares of our common stock issued and outstanding.

We operate as a REIT for U.S. federal income tax purposes. To remain qualified and be taxed as a REIT, we are generally required to annually distribute to our stockholders at least 90% of our REIT taxable income (determined without regard to the dividends paid deduction, excluding net capital gain and after the utilization of any available NOLs).

We declared quarterly cash dividends of $1.05 per share of common stock in the first quarter of 2018, which were paid on March 30, 2018. The declaration, amount and payment of any future dividends, however, are subject to the determination and approval of our board of directors based on then current or anticipated future conditions, including our earnings, net cash provided by operating activities, capital requirements, financial condition, our relative market capitalization, our existing federal NOLs or other factors deemed relevant by our board of directors. See “Risk Factors—Risks Relating to Our REIT Status.” In addition, our ability to pay dividends is limited by the terms of our debt instruments and our Mandatory Convertible Preferred Stock under certain circumstances.

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DESCRIPTION OF CAPITAL STOCK

The following is a description of certain general terms and provisions of our capital stock. The following summary does not purport to be complete, and is subject to, and qualified in its entirety by, our Restated Certificate of Incorporation (“Charter”), our amended and restated by-laws (“By-laws”), the General Corporation Law of the State of Delaware (“DGCL”), the Certificate of Designations of our Mandatory Convertible Preferred Stock (“Certificate of Designations”) and, for any other series of preferred stock, the certificate of designations relating to such particular series of preferred stock. Copies of our Charter, By-laws and the Certificate of Designations have been filed as exhibits to SEC filings incorporated by reference in this prospectus supplement. You are urged to read the Charter, the By-laws and the Certificate of Designations in their entirety. As used in this Section, unless otherwise expressly stated or the context otherwise requires, the terms “Company,” “Crown Castle,” “we,” “our” and “us” refer to Crown Castle International Corp. and not to any of its subsidiaries.

The information appearing under this caption “Description of Capital Stock” supplements and, to the extent inconsistent, replaces the information appearing in the accompanying prospectus under the caption “Description of Capital Stock.” You should read the following description of our capital stock in light of this information and the other information under “Risk Factors” in this prospectus supplement.

General

Our authorized capital stock consists of 600,000,000 shares of common stock, par value $0.01 per share, and 20,000,000 shares of preferred stock, par value $0.01 per share. As of April 4, 2018, there were 414,822,516 shares of our common stock outstanding and 1,649,998 shares of our Mandatory Convertible Preferred Stock outstanding.

Our common stock is listed for trading on the NYSE under the trading symbol “CCI” and our Mandatory Convertible Preferred Stock is listed for trading on the NYSE under the trading symbol “CCI-PA.”

Common Stock

Voting Rights

Each share of our common stock is entitled to one vote. Holders of our common stock vote together as a single class on all matters presented for a vote of the stockholders, except as provided under the DGCL. See also “—Charter and By-laws—Election and Removal of Directors” below.

Dividends and Liquidation Rights

Each share of our common stock is entitled to receive dividends if, as and when declared by our board of directors out of funds legally available for that purpose, subject to certain rights of holders of preferred stock, including the rights of holders of Mandatory Convertible Preferred Stock. In the event of our voluntary or involuntary liquidation, dissolution or winding up, after satisfaction of amounts payable to our creditors and distribution of any preferential amounts to the holders of outstanding preferred stock, including Mandatory Convertible Preferred Stock, holders of our common stock are entitled to share ratably in the assets available for distribution to the stockholders.

Other Provisions

The holders of our common stock have no preemptive, subscription or redemption rights and are not entitled to the benefit of any sinking fund. All outstanding shares of common stock are validly issued, fully paid and nonassessable. Under the DGCL, stockholders generally are not personally liable for a corporation’s acts or debts.

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Preferred Stock

Under the Charter, our board of directors is authorized, without further stockholder action, to issue up to 20,000,000 shares of preferred stock, par value $0.01 per share, in one or more series by filing a certificate of designations with the Secretary of State of the State of Delaware. Such certificate of designations may set forth the designations, powers, preferences and rights of the shares of each such series of preferred stock and the qualifications, limitations and restrictions thereof, including the dividend rate, the redemption provisions, if any, the amount payable in the event of our voluntary or involuntary liquidation, winding-up or dissolution, the terms and conditions, if any, of conversion and the voting rights. We have filed the Certificate of Designations with the Secretary of State of the State of Delaware to create the Mandatory Convertible Preferred Stock described below.

Mandatory Convertible Preferred Stock

The Mandatory Convertible Preferred Stock is a series of our preferred stock and impacts the rights of holders of our common stock. Each share of Mandatory Convertible Preferred Stock, unless previously converted, will automatically convert on August 1, 2020 into a number of shares of our common stock based on a specified conversion rate, which is subject to adjustment from time to time. The dividend on the Mandatory Convertible Preferred Stock, when, as and if declared, is $17.1875 per share (based on the annual dividend rate of 6.875% and a liquidation preference of $1,000.00 per share). Declared dividends on the Mandatory Convertible Preferred Stock are payable quarterly on February 1, May 1, August 1 and November 1 of each year to and including August 1, 2020. A further description of the terms of our Mandatory Convertible Preferred Stock is set forth in the Capital Stock Description (as defined in “—Where You Can Find More Information”) and incorporated by reference herein and is subject to, and qualified in its entirety by, the full terms of the Certificate of Designations contained in Exhibit 4.2 to the registration statement of which this prospectus supplement forms a part.

Charter and By-laws

Stockholders’ rights and related matters are governed by the DGCL, our Charter and our By-laws. Certain provisions of our Charter and By-laws, descriptions of which are summarized or otherwise incorporated within this prospectus supplement and the accompanying prospectus, may have the effect, either alone or in combination with each other, of discouraging or making more difficult a tender offer or takeover attempt that is opposed by our board of directors but that a stockholder might consider to be in its best interest. Such provisions may also adversely affect prevailing market prices for our capital stock. We believe that such provisions are necessary to enable us to develop our business in a manner that will foster our long-term growth without disruption caused by the threat of a takeover not deemed by our board of directors to be in our best interests and those of our stockholders.

Election and Removal of Directors

The Charter provides for the annual election of directors on our board of directors.

The Charter also provides that any director, except for directors who may be elected by the holders of any series of preferred stock, may be removed from office at any time, with or without cause, only by the affirmative vote of the holders of at least 80% of the voting power of the then outstanding Voting Stock, voting together as a single class. “Voting Stock” is defined in the Charter as the outstanding shares of our capital stock entitled to vote in a general vote of our stockholders as a single class with shares of our common stock.

Proxy Access

Our By-laws also contain a proxy access right provision, which permits a stockholder, or group of up to 20 stockholders, who owns (and continues to own) 3% or more of our common stock and has continuously owned our common stock for at least three years to nominate and include in our proxy materials candidates for election as directors of the Company. Such stockholders or groups of stockholders may nominate up to the greater of two individuals or 20% of the board of directors, provided that the stockholders and the nominees satisfy the notice and other procedural requirements specified in the By-laws.

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Ownership Limitations and Transfer Restrictions

To facilitate our continued qualification as a REIT under the Code, the Charter contains ownership limitations and transfer restrictions on our capital stock. These ownership limitations and transfer restrictions could have the effect of delaying, deferring or preventing a transaction or a change in control of us that might involve a premium price for our capital stock or otherwise be in the best interest of our stockholders. All certificates representing shares of capital stock bear a legend describing such ownership limitations and transfer restrictions.

In order for us to continue to satisfy the requirements for REIT qualification, our capital stock must be beneficially owned by 100 or more persons during at least 335 days of a taxable year of 12 months or during a proportionate part of a shorter taxable year. Also, not more than 50% of the value of the outstanding shares of our capital stock may be owned, directly or indirectly, by five or fewer “individuals” (as defined in the Code to include certain entities such as private foundations) during the last half of a taxable year. To satisfy these ownership requirements and other requirements for continued qualification as a REIT and to otherwise protect us from the consequences of a concentration of ownership among our stockholders, the Charter contains provisions limiting the ownership and restricting the transfer of shares of our capital stock.

The relevant section of the Charter provides that, among other things and subject to certain exceptions, no “Person” (as defined in the Charter) may beneficially or constructively own, or be deemed to beneficially or constructively own by virtue of the attribution provisions of the Code, more than 9.8%, by value or number of shares, whichever is more restrictive, of the outstanding shares of our common stock (which restriction we refer to as the “common stock ownership limit”), or 9.8% in aggregate value of the outstanding shares of all classes and series of our capital stock, including our common stock and Mandatory Convertible Preferred Stock (which restriction we refer to as the “aggregate stock ownership limit”).

The Charter also prohibits:

• any person from beneficially owning shares of our capital stock to the extent that such beneficial ownership would result in our being “closely held” within the meaning of Section 856(h) of the Code (without regard to whether the ownership interest is held during the last half of a taxable year);

• any person from beneficially or constructively owning shares of our capital stock to the extent that such beneficial or constructive ownership would otherwise result in our failing to qualify as a REIT (including, but not limited to, beneficial ownership or constructive ownership that would result in our actually owning or constructively owning an interest in a tenant that is described in Section 856(d)(2)(B) of the Code if the income derived by us from such tenant would cause us to fail to satisfy any of the gross income requirements of Section 856(c) of the Code);

• any person from beneficially or constructively owning shares of our capital stock to the extent such beneficial or constructive ownership could result in our failing to qualify as a “domestically controlled qualified investment entity” within the meaning of Section 897(h)(4)(B) of the Code; and

• any person from transferring shares of our capital stock if such transfer would result in shares of our capital stock being beneficially owned by fewer than 100 persons (determined under the principles of Section 856(a)(5) of the Code).

The foregoing provisions on transferability and ownership, including the aggregate stock ownership limit and common stock ownership limit, will not apply if our board of directors determines that it is no longer in our best interests to continue to qualify as a REIT.

For additional and more detailed information, please see “Description of Capital Stock—Charter and By-Laws—Ownership Limitations and Transfer Restrictions” in the accompanying prospectus and the description of our capital stock set forth in the Capital Stock Description and incorporated by reference herein.

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MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

The following is a summary of the material U.S. federal income tax consequences of an investment in our common stock. This summary is based upon the Code, the regulations promulgated by the Treasury, rulings and other administrative pronouncements issued by the Internal Revenue Service (“IRS”), and judicial decisions, all as currently in effect, and all of which are subject to differing interpretations or to change, possibly with retroactive effect. No assurance can be given that the IRS would not assert, or that a court would not sustain, a position contrary to any of the tax consequences described below. The summary is also based upon the assumption that we and our subsidiaries and affiliated entities will operate in accordance with our and their applicable organizational documents. This summary is for general information only and is not tax advice. It does not discuss any state, local or non-U.S. tax consequences relevant to us or an investment in our common stock, and it does not purport to discuss all aspects of U.S. federal income taxation that may be important to a particular investor in light of its investment or tax circumstances or to investors subject to special tax rules, such as:

• financial institutions;

• insurance companies;

• broker-dealers;

• regulated investment companies;

• passive foreign investment companies;

• controlled foreign corporations;

• companies that accumulate earnings to avoid U.S. federal income tax;

• U.S. expatriates;

• former long-term permanent residents of the United States;

• partnerships, other pass-through entities and trusts;

• persons who hold our common stock on behalf of other persons as nominees;

• persons who receive our common stock in connection with employment or other performance of services;

• persons holding our common stock as part of a “straddle,” “hedge,” “conversion transaction,” “synthetic security” or other integrated investment; and, except to the extent discussed below:

• REITs;

• tax-exempt organizations; and

• foreign investors.

This summary assumes that investors will hold their common stock as a capital asset, which generally means property held for investment.

Your federal income tax consequences may depend on whether or not you are a “U.S. stockholder.” For purposes of this summary, a “U.S. stockholder” is any holder of our common stock that is, for U.S. federal income tax purposes:

• an individual who is a citizen or resident of the United States;

• a corporation (or entity treated as a corporation for U.S. federal income tax purposes) created or organized in the United States or under the laws of the United States, or of any state thereof, or the District of Columbia;

• an estate, the income of which is includable in gross income for U.S. federal income tax purposes regardless of its source; or

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• a trust if (i) a U.S. court is able to exercise primary supervision over the administration of the trust and one or more U.S. fiduciaries have the authority to control all substantial decisions of the trust or (ii) it has a valid election in effect under applicable Treasury regulations to be treated as a “U.S. person.”

A “non-U.S. stockholder” is any holder of our common stock other than a partnership or U.S. stockholder. If a partnership, including for this purpose any entity or arrangement that is treated as a partnership for U.S. federal income tax purposes, holds our common stock, the tax treatment of a partner in the partnership will generally depend upon the status of the partner and the activities of the partnership. An investor that is a partnership and the partners in such partnership should consult their tax advisors about the U.S. federal income tax consequences of the acquisition, ownership and disposition of our common stock.

The U.S. federal income tax treatment of holders of our common stock depends in some instances on determinations of fact and interpretations of complex provisions of U.S. federal income tax law for which no clear precedent or authority may be available. In addition, the tax consequences to any particular stockholder of holding or disposing of our common stock will depend on the stockholder’s particular tax circumstances. You are urged to consult your tax advisor regarding the U.S. federal, state, local, and foreign income and other tax consequences to you in light of your particular investment or tax circumstances of acquiring, holding, exchanging, or otherwise disposing of our common stock.

Taxation of Crown Castle

We elected to be taxed as a REIT commencing with the taxable year ended December 31, 2014, and intend to continue to operate in a manner that will allow us to continue to qualify as a REIT.

The law firms of Cravath, Swaine & Moore LLP and Skadden, Arps, Slate, Meagher & Flom LLP each have acted as our REIT tax counsel (“Tax Counsel”). We have received opinions from our Tax Counsel to the effect that, commencing with our taxable year ended December 31, 2014, we have been organized and have operated in conformity with the requirements for qualification and taxation as a REIT under the Code, and that our proposed method of operation will enable us to meet the requirements for qualification and taxation as a REIT. It must be emphasized that the opinions of our Tax Counsel are based on various assumptions relating to our organization and operation and are conditioned upon fact-based representations and covenants made by our management regarding our organization, assets, income, and the present and future conduct of our business operations. While we intend to operate so that we will continue to qualify as a REIT, given the highly complex nature of the rules governing REITs, the ongoing importance of factual determinations, and the possibility of future changes in our circumstances, no assurance can be given by our Tax Counsel or by us that we will qualify as a REIT for any particular year. The opinions are each expressed as of the date issued. Our Tax Counsel will have no obligation to advise us or our stockholders of any subsequent change in the matters stated, represented or assumed, or of any subsequent change in the applicable law. You should be aware that opinions of counsel are not binding on the IRS, and no assurance can be given that the IRS will not challenge the conclusions set forth in such opinions.

Qualification and taxation as a REIT depends on our ability to meet on a continuing basis, through actual operating results, distribution levels, and diversity of stock ownership, various qualification requirements imposed upon REITs by the Code, the results of which have not been and will not be reviewed by our Tax Counsel. Our ability to qualify as a REIT also requires that we satisfy certain asset tests, some of which depend upon the fair market values of assets that we own directly or indirectly. Such values may not be susceptible to a precise determination. Accordingly, no assurance can be given that the actual results of our operations for any taxable year have satisfied or will satisfy such requirements for qualification and taxation as a REIT.

Taxation of REITs in General

As indicated above, our qualification and taxation as a REIT depends upon our ability to meet, on a continuing basis, various qualification requirements imposed upon REITs by the Code. The material qualification requirements are summarized below under “—Requirements for Qualification—General.” While we intend to

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operate so that we continue to qualify as a REIT, no assurance can be given that the IRS will not challenge our qualification, or that we will be able to operate in accordance with the REIT requirements in the future. See “—Failure to Qualify.”

Provided that we continue to qualify as a REIT, generally we will be entitled to a deduction for dividends that we pay and therefore will not be subject to U.S. federal corporate income tax on our net taxable income that is currently distributed to our stockholders. This treatment substantially eliminates the “double taxation” at the corporate and stockholder levels that generally results from an investment in a C corporation. A “C corporation” is a corporation that generally is required to pay tax at the corporate level. Double taxation means taxation once at the corporate level when income is earned and once again at the stockholder level when the income is distributed. In general, the income that we generate is taxed only at the stockholder level upon a distribution of dividends to our stockholders.

Most U.S. stockholders that are individuals, trusts or estates are taxed on corporate dividends at a maximum U.S. federal income tax rate of 20% (the same as long-term capital gains). With limited exceptions, however, dividends from us or from other entities that are taxed as REITs are generally not eligible for this rate and will continue to be taxed at rates applicable to ordinary income. The highest marginal non-corporate U.S. federal income tax rate applicable to ordinary income is 37%. For taxable years beginning after December 31, 2017 and before January 1, 2026, generally, stockholders that are individuals, trusts or estates may deduct 20% of the aggregate amount of ordinary dividends distributed by us, subject to certain limitations. See “—Taxation of Stockholders—Taxation of Taxable U.S. Stockholders—Distributions.”

Any net operating losses, foreign tax credits and other tax attributes generally do not pass through to our stockholders, subject to special rules for certain items such as capital gains that we recognize. See “—Taxation of Stockholders—Taxation of Taxable U.S. Stockholders—Distributions.”

If we qualify as a REIT, we will nonetheless be subject to U.S. federal tax in the following circumstances:

• We will be taxed at regular corporate rates on any undistributed net taxable income, including undistributed net capital gains.

• If we have net income from prohibited transactions, which are, in general, sales or other dispositions of inventory or property held primarily for sale to customers in the ordinary course of business, other than foreclosure property, such income will be subject to a 100% tax. See “—Prohibited Transactions” and “—Foreclosure Property” below.

• If we elect to treat property that we acquire in connection with a foreclosure of a mortgage loan or certain leasehold terminations as “foreclosure property,” we may thereby avoid the 100% tax on gain from a resale of that property (if the sale would otherwise constitute a prohibited transaction), but the income from the sale or operation of the property may be subject to corporate income tax at the highest applicable rate (currently 21%).

• If we fail to satisfy the 75% gross income test or the 95% gross income test, as discussed below, but nonetheless maintain our qualification as a REIT because we satisfy other requirements, we will be subject to a 100% tax on an amount based on the magnitude of the failure, as adjusted to reflect the profit margin associated with our gross income.

• If we violate the asset tests (other than certain de minimis violations) or other requirements applicable to REITs, as described below, and yet maintain our qualification as a REIT because there is reasonable cause for the failure and other applicable requirements are met, we may be subject to a penalty tax. In that case, the amount of the penalty tax will be at least $50,000 per failure, and, in the case of certain asset test failures, will be determined as the amount of net income generated by the nonqualifying assets in question multiplied by the highest corporate tax rate (currently 21%) if that amount exceeds $50,000 per failure.

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• If we fail to distribute during each calendar year at least the sum of (i) 85% of our REIT ordinary income for such year, (ii) 95% of our REIT capital gain net income for such year and (iii) any undistributed net taxable income from prior periods, we will be subject to a nondeductible 4% excise tax on the excess of the required distribution over the sum of (a) the amounts that we actually distributed and (b) the amounts we retained and upon which we paid income tax at the corporate level.

• We may be required to pay monetary penalties to the IRS in certain circumstances, including if we fail to meet record-keeping requirements intended to monitor our compliance with rules relating to the composition of a REIT’s stockholders, as described below in “—Requirements for Qualification—General.”

• A 100% tax may be imposed on transactions between us and a TRS (as defined below) that do not reflect arm’s length terms.

• If we acquire appreciated assets from a corporation that is not a REIT (i.e., a corporation taxable under subchapter C of the Code) in a transaction in which the adjusted tax basis of the assets in our hands is determined by reference to the adjusted tax basis of the assets in the hands of the subchapter C corporation, including assets owned by us at the effective date of our election to be taxed as a REIT, we may be subject to tax on such appreciation at the highest corporate income tax rate then applicable if we subsequently recognize gain on a disposition of any such assets during a period of up to five-years following their acquisition from the subchapter C corporation.

• The earnings of our taxable REIT subsidiaries (“TRSs”) generally will be subject to U.S. federal corporate income tax.

In addition, we and our subsidiaries may be subject to a variety of taxes, including payroll taxes and state, local, and foreign income, property, gross receipts, franchise and other taxes on our assets and operations. We could also be subject to tax in situations and on transactions not presently contemplated.

Requirements for Qualification—General

The Code defines a REIT as a corporation, trust or association:

1. that is managed by one or more trustees or directors;

2. the beneficial ownership of which is evidenced by transferable shares, or by transferable certificates of beneficial interest;

3. that would be taxable as a domestic corporation but for its election to be subject to tax as a REIT;

4. that is neither a financial institution nor an insurance company subject to specific provisions of the Code;

5. the beneficial ownership of which is held by 100 or more persons;

6. in which, during the last half of each taxable year, not more than 50% in value of the outstanding stock is owned, directly or indirectly, by five or fewer “individuals” (as defined in the Code to include specified tax-exempt entities); and

7. that meets other tests described below, including with respect to the nature of its income and assets.

The Code provides that conditions (1) through (4) must be met during the entire taxable year, and that condition (5) must be met during at least 335 days of a taxable year of 12 months, or during a proportionate part of a shorter taxable year. Conditions (5) and (6) need not be met during a corporation’s initial tax year as a REIT (which, in our case, was 2014). We have put limitations and restrictions into place regarding the ownership and transfer of our stock, which are intended to assist us in satisfying the stock ownership requirements described in conditions (5) and (6) above. See “Risk Factors—Risks Relating to Our REIT Status” and “Description of Capital Stock—Ownership Limitations and Transfer Restrictions.” These restrictions, however, may not ensure

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that we will, in all cases, be able to satisfy the share ownership requirements described in conditions (5) and (6) above. If we fail to satisfy these share ownership requirements, except as provided in the next sentence, our status as a REIT will terminate. If, however, we comply with the rules contained in applicable Treasury regulations that require us to ascertain the actual ownership of our shares and we do not know, or would not have known through the exercise of reasonable diligence, that we failed to meet the requirement described in condition (6) above, we will be treated as having met this requirement.

To monitor compliance with the stock ownership requirements, we generally are required to maintain records regarding the actual ownership of our stock. To do so, we must demand written statements each year from the record holders of significant percentages of our stock pursuant to which the record holders must disclose the actual owners of the stock (i.e., the persons required to include our dividends in their gross income). We must maintain a list of those persons failing or refusing to comply with this demand as part of our records. We could be subject to monetary penalties if we fail to comply with these record-keeping requirements. If you fail or refuse to comply with the demands, you will be required by Treasury regulations to submit a statement with your tax return disclosing your actual ownership of our stock and other information.

In addition, a REIT generally must use the calendar year as its taxable year. Our taxable year is the calendar year, so we satisfy this requirement.

Effect of Subsidiary Entities

Ownership of Partnership Interests. If we are a partner in an entity that is treated as a partnership for U.S. federal income tax purposes, Treasury regulations provide that we are deemed to own our proportionate share of the partnership’s assets, and to earn our proportionate share of the partnership’s income, for purposes of the asset and gross income tests applicable to REITs. Our proportionate share of a partnership’s assets and income is based on our capital interest in the partnership (except that for purposes of the 10% value test, described below, our proportionate share of the partnership’s assets is based on our proportionate interest in the equity and certain debt securities issued by the partnership). In addition, the assets and gross income of the partnership are deemed to retain the same character in our hands. Thus, our proportionate share of the assets and items of income of any of our subsidiary partnerships will be treated as our assets and items of income for purposes of applying the REIT requirements.

Disregarded Subsidiaries. If we own a corporate subsidiary that is a “qualified REIT subsidiary,” that subsidiary is generally disregarded as a separate entity for U.S. federal income tax purposes, and all of the subsidiary’s assets, liabilities and items of income, deduction and credit are treated as our assets, liabilities and items of income, deduction and credit, including for purposes of the gross income and asset tests applicable to REITs. A qualified REIT subsidiary is any corporation, other than a TRS (as described below), that is directly or indirectly wholly owned by a REIT. Other entities that are wholly owned by us, including single member limited liability companies that have not elected to be taxed as corporations for U.S. federal income tax purposes, are also generally disregarded as separate entities for U.S. federal income tax purposes, including for purposes of the REIT income and asset tests. Disregarded subsidiaries, along with any partnerships in which we hold an equity interest, are sometimes referred to herein as “pass-through subsidiaries.”

In the event that a disregarded subsidiary of ours ceases to be wholly owned—for example, if any equity interest in the subsidiary is acquired by a person other than us or another disregarded subsidiary of ours—the subsidiary’s separate existence would no longer be disregarded for U.S. federal income tax purposes. Instead, the subsidiary would have multiple owners and would be treated as either a partnership or a taxable corporation. Such an event could, depending on the circumstances, adversely affect our ability to satisfy the various asset and gross income requirements applicable to REITs, including the requirement that REITs generally may not own, directly or indirectly, more than 10% of the securities of another corporation. See “—Income Tests” and “—Asset Tests.”

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Taxable REIT Subsidiaries. In general, we may jointly elect with a subsidiary corporation, whether or not wholly owned, to treat such subsidiary corporation as a TRS. We generally may not own more than 10% of the securities of a taxable corporation, as measured by voting power or value, unless we and such corporation elect to treat such corporation as a TRS. The separate existence of a TRS or other taxable corporation is not ignored for U.S. federal income tax purposes. Accordingly, a TRS or other taxable subsidiary corporation generally is subject to corporate income tax on its earnings, which may reduce the cash flow that we and our subsidiaries generate in the aggregate, and may reduce our ability to make distributions to our stockholders.

We are not treated as holding the assets of a TRS or other taxable subsidiary corporation or as receiving any income that the subsidiary earns. Rather, the stock issued by a taxable subsidiary corporation to us is an asset in our hands, and we treat the dividends paid to us from such taxable subsidiary corporation, if any, as income. This treatment can affect our income and asset test calculations, as described below. Because we do not include the assets and income of TRSs or other taxable subsidiary corporations on a look-through basis in determining our compliance with the REIT requirements, we may use such entities to undertake indirectly activities that the REIT rules might otherwise preclude us from doing directly or through pass-through subsidiaries. For example, we may use TRSs or other taxable subsidiary corporations to perform services or conduct activities that give rise to certain categories of income such as management fees, or to conduct activities that, if conducted by us directly, would be treated in our hands as prohibited transactions.

The TRS rules limit the deductibility of interest paid or accrued by a TRS to its parent REIT to assure that the TRS is subject to an appropriate level of corporate taxation. Further, the rules impose a 100% excise tax on transactions between a TRS and its parent REIT or the REIT’s tenants that are not conducted on an arm’s length basis. We intend that all of our transactions with our TRSs, if any, will be conducted on an arm’s length basis.

Income Tests

In order to maintain our qualification as a REIT, we must satisfy two gross income requirements on an annual basis. First, at least 75% of our gross income for each taxable year, excluding gross income from sales of inventory or dealer property in “prohibited transactions,” discharge of indebtedness and certain hedging transactions, generally must be derived from “rents from real property,” gains from the sale of real property, mortgages on real property and shares in other REITs, interest income derived from mortgage loans secured by real property (including certain types of mortgage-backed securities), dividends received from other REITs, and specified income from temporary investments. Second, at least 95% of our gross income in each taxable year, excluding gross income from prohibited transactions, discharge of indebtedness and certain hedging transactions, must be derived from some combination of income that qualifies under the 75% gross income test described above, as well as other dividends, interest, and gain from the sale or disposition of stock or securities, which need not have any relation to real property. Income and gain from certain hedging transactions will be excluded from both the numerator and the denominator for purposes of both the 75% and 95% gross income tests.

Rents from Real Property. Rents we receive from a tenant will qualify as “rents from real property” for the purpose of satisfying the gross income requirements for a REIT described above only if all of the conditions described below are met.

• The amount of rent is not based in whole or in part on the income or profits of any person. However, an amount we receive or accrue generally will not be excluded from the term “rents from real property” solely because it is based on a fixed percentage or percentages of receipts or sales;

• Neither we nor an actual or constructive owner of 10% or more of our stock actually or constructively owns 10% or more of the interests in the assets or net profits of a non-corporate tenant, or, if the tenant is a corporation, 10% or more of the total combined voting power of all classes of stock entitled to vote or 10% or more of the total value of all classes of stock of the tenant. Rents we receive from such a tenant that is a TRS of ours, however, will not be excluded from the definition of “rents from real property” as a result of this condition if at least 90% of the space at the property to which the rents

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relate is leased to third parties, and the rents paid by the TRS are substantially comparable to rents paid by our other tenants for comparable space. Whether rents paid by a TRS are substantially comparable to rents paid by other tenants is determined at the time the lease with the TRS is entered into, extended, and modified, if such modification increases the rents due under such lease. Notwithstanding the foregoing, however, if a lease with a “controlled TRS” is modified and such modification results in an increase in the rents payable by such TRS, any such increase will not qualify as “rents from real property.” For purposes of this rule, a “controlled TRS” is a TRS in which the parent REIT owns stock possessing more than 50% of the voting power or more than 50% of the total value of the outstanding stock of such TRS;

• Rent attributable to personal property that is leased in connection with a lease of real property is not greater than 15% of the total rent received under the lease. If this condition is not met, then the portion of the rent attributable to personal property will not qualify as “rents from real property”; and

• We generally do not operate or manage the property or furnish or render services to our tenants, subject to a 1% de minimis exception and except as provided below. We are permitted, however, to perform directly certain services that are “usually or customarily rendered” in connection with the rental of space for occupancy only and are not otherwise considered “rendered to the occupant” of the property. In addition, we are permitted to employ an independent contractor from whom we derive no revenue to provide customary services to our tenants, or a TRS, which may be wholly or partially owned by us, to provide both customary and non-customary services to our tenants without causing the rent that we receive from those tenants to fail to qualify as “rents from real property.”

We believe that substantially all of the services we render with respect to our shared communications infrastructure are of the type that are usually or customarily performed in connection with the rental of communications infrastructure and are not primarily for the benefit or convenience of our tenants. Therefore, we believe that our provision of these services will not cause rents received with respect to our properties to fail to qualify as “rents from real property.” We intend to cause any services that are not “usually or customarily rendered,” or that are for the benefit of a particular tenant in connection with the rental of real property, to be provided through a TRS or through an “independent contractor.” However, no assurance can be given that the IRS will concur with our determination as to whether a particular service is usual or customary, or otherwise in this regard.

Interest Income. Interest income constitutes qualifying mortgage interest for purposes of the 75% gross income test (as described above) to the extent that the obligation upon which such interest is paid is secured by a mortgage on real property. If we receive interest income with respect to a mortgage loan that is secured by both real property and other property, and the highest principal amount of the loan outstanding during a taxable year exceeds the fair market value of the real property on the date that we acquired or originated the mortgage loan, the interest income generally will be apportioned between the real property and the other collateral, and our income from the arrangement will qualify for purposes of the 75% gross income test only to the extent that the interest is allocable to the real property. In certain cases, personal property collateral that secures a loan may be treated as real property for purposes of the foregoing rules. Even if a loan is not secured by real property, or is under-secured, the income that it generates may nonetheless qualify for purposes of the 95% gross income test. For these purposes, the term “interest” generally does not include any amount received or accrued, directly or indirectly, if the determination of all or some of the amount depends in any way on the income or profits of any person. However, an amount received or accrued generally will not be excluded from the term “interest” solely by reason of being based on a fixed percentage or percentages of receipts or sales.

Dividend Income. We may directly or indirectly receive distributions from TRSs or other corporations that are not REITs or qualified REIT subsidiaries. These distributions generally are treated as dividend income to the extent of the earnings and profits of the distributing corporation. Such distributions will generally constitute qualifying income for purposes of the 95% gross income test, but not for purposes of the 75% gross income test. Any dividends that we receive from another REIT, however, will be qualifying income for purposes of both the 95% and 75% gross income tests.

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Fee Income. Any fee income that we earn generally will not be qualifying income for purposes of either gross income test. Any fees earned by a TRS, however, will not be included for purposes of our gross income tests.

Hedging Transactions. Any income or gain that we or our pass-through subsidiaries derive from instruments that hedge certain risks, such as the risk of changes in interest rates, will be excluded from gross income for purposes of both the 75% and 95% gross income tests, provided that specified requirements are met, including the requirement that the instrument is entered into during the ordinary course of our business and is properly identified as a hedge, along with the risk that it hedges, within prescribed time periods. Income and gain from all other hedging transactions will not be qualifying income for either the 95% or 75% gross income test.

Failure to Satisfy the Gross Income Tests. If we fail to satisfy one or both of the 75% or 95% gross income tests for any taxable year, we may still qualify as a REIT for such year if we are entitled to relief under applicable provisions of the Code. These relief provisions will be generally available if (i) our failure to meet these tests was due to reasonable cause and not due to willful neglect and (ii) following our identification of the failure to meet the 75% or 95% gross income test for any taxable year, we file a schedule with the IRS setting forth each item of our gross income for purposes of the 75% or 95% gross income test for such taxable year in accordance with Treasury regulations, which have not yet been issued. It is not possible to state whether we would be entitled to the benefit of these relief provisions in all circumstances. If these relief provisions are inapplicable to a particular set of circumstances, we will not qualify as a REIT. Even if these relief provisions apply, and we retain our status as a REIT, the Code imposes a tax based upon the amount by which we fail to satisfy the particular gross income test.

Asset Tests

At the close of each calendar quarter, we must also satisfy five tests relating to the nature of our assets. First, at least 75% of the value of our total assets must be represented by some combination of “real estate assets,” cash, cash items, U.S. government securities, and, under some circumstances, stock or debt instruments purchased with new capital. For this purpose, real estate assets include interests in real property, stock of other corporations that qualify as REITs, certain kinds of mortgage-backed securities and mortgage loans, and debt instruments (whether or not secured by real property) that are issued by a “publicly offered REIT” (i.e., a REIT that is required to file annual and period reports with the SEC under the Exchange Act. Assets that do not qualify for purposes of the 75% asset test are subject to the additional asset tests described below.

Second, the value of any one issuer’s securities that we own may not exceed 5% of the value of our total assets.

Third, we may not own more than 10% of any one issuer’s outstanding securities, as measured by either voting power or value. The 5% and 10% asset tests do not apply to securities of TRSs and qualified REIT subsidiaries and the 10% value test does not apply to “straight debt” having specified characteristics and to certain other securities described below. Solely for purposes of the 10% value test, the determination of our interest in the assets of a partnership or limited liability company in which we own an interest will be based on our proportionate interest in any securities issued by the partnership or limited liability company, excluding for this purpose certain securities described in the Code.

Fourth, the aggregate value of all securities of TRSs that we hold may not exceed 20% of the value of our total assets.

Fifth, no more than 25% of the total value of our assets may be represented by “nonqualified publicly offered REIT debt instruments” (i.e., real estate assets that would cease to be real estate assets if debt instruments issued by publicly offered REITs were not included in the definition of real estate assets).

Notwithstanding the general rule, as noted above, that for purposes of the REIT income and asset tests we are treated as owning our proportionate share of the underlying assets of a subsidiary partnership, if we hold

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indebtedness issued by a partnership, the indebtedness will be subject to, and may cause a violation of, the asset tests unless the indebtedness is a qualifying mortgage asset or other conditions are met. Similarly, although stock of another REIT is a qualifying asset for purposes of the REIT asset tests, any non-mortgage debt that is issued by a non-publicly offered REIT may not so qualify (although such debt will not be treated as “securities” for purposes of the 10% value test, as explained below).

Certain securities will not cause a violation of the 10% value test described above. Such securities include instruments that constitute “straight debt,” which term generally excludes, among other things, securities having contingency features. A security does not qualify as “straight debt” where a REIT (or a controlled TRS of the REIT) owns other securities of the same issuer which do not qualify as straight debt, unless the value of those other securities constitute, in the aggregate, 1% or less of the total value of that issuer’s outstanding securities. In addition to straight debt, the Code provides that certain other securities will not violate the 10% value test. Such securities include (i) any loan made to an individual or an estate, (ii) certain rental agreements pursuant to which one or more payments are to be made in subsequent years (other than agreements between a REIT and certain persons related to the REIT under attribution rules), (iii) any obligation to pay rents from real property, (iv) securities issued by governmental entities that are not dependent in whole or in part on the profits of (or payments made by) a non-governmental entity, (v) any security (including debt securities) issued by another REIT and (vi) any debt instrument issued by a partnership if the partnership’s income is of a nature that it would satisfy the 75% gross income test described above under “—Income Tests.” In applying the 10% value test, a debt security issued by a partnership is not taken into account to the extent, if any, of the REIT’s proportionate interest in the equity and certain debt securities issued by that partnership.

No independent appraisals have been obtained to support our conclusions as to the value of our total assets or the value of any particular security or securities. Moreover, the values of some assets may not be susceptible to a precise determination, and values are subject to change in the future. Furthermore, the proper classification of an instrument as debt or equity for U.S. federal income tax purposes may be uncertain in some circumstances, which could affect the application of the REIT asset requirements. Accordingly, there can be no assurance that the IRS will not contend that our interests in our subsidiaries or in the securities of other issuers will not cause a violation of the REIT asset tests.

However, certain relief provisions are available to allow REITs to satisfy the asset test requirements or to maintain REIT qualification notwithstanding certain violations of the asset tests and other requirements. For example, if we should fail to satisfy the asset tests at the end of a calendar quarter, such a failure would not cause us to lose our REIT qualification if (i) we satisfied the asset tests at the close of the preceding calendar quarter and (ii) the discrepancy between the value of our assets and the asset test requirements was not wholly or partly caused by an acquisition of non-qualifying assets, but instead arose from changes in the relative market values of our assets. If the condition described in clause (ii) were not satisfied, we still could avoid disqualification by eliminating any discrepancy within 30 days after the close of the calendar quarter in which it arose or by making use of the relief provisions described above.

In the case of de minimis violations of the 10% and 5% asset tests, a REIT may maintain its qualification despite a violation of such requirements if (i) the value of the assets causing the violation does not exceed the lesser of 1% of the REIT’s total assets and $10,000,000 and (ii) the REIT either disposes of the assets causing the failure within six months after the last day of the quarter in which it identifies the failure, or the relevant tests are otherwise satisfied within that time frame.

Even if we did not qualify for the foregoing relief provisions, one additional provision allows a REIT which fails one or more of the asset requirements to nevertheless maintain its REIT qualification if (i) the REIT provides the IRS with a description of each asset causing the failure, (ii) the failure is due to reasonable cause and not willful neglect, (iii) the REIT pays a tax equal to the greater of (a) $50,000 per failure and (b) the product of the net income generated by the assets that caused the failure multiplied by the highest applicable corporate tax rate (currently 21%) and (iv) the REIT either disposes of the assets causing the failure within six months after

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the last day of the quarter in which it identifies the failure, or otherwise satisfies the relevant asset tests within that time frame.

Annual Distribution Requirements

In order to qualify as a REIT, we are required to distribute dividends, other than capital gain dividends, to our stockholders in an amount at least equal to:

1. the sum of

a. 90% of our REIT taxable income, computed without regard to our net capital gains and the deduction for dividends paid; and

b. 90% of our after tax net income, if any, from foreclosure property (as described below); minus

2. the excess of the sum of specified items of non-cash income over 5% of our REIT taxable income, computed without regard to our net capital gains and the deduction for dividends paid.

We generally must make these distributions in the taxable year to which they relate, or in the following taxable year if declared before we timely file our tax return for the year and if paid with or before the first regular distribution payment after such declaration. These distributions generally will be treated as received by our stockholders in the year in which paid.

To the extent that we distribute at least 90%, but less than 100%, of our REIT taxable income, as adjusted, we will be subject to tax at ordinary corporate tax rates on the retained portion. We may elect to retain, rather than distribute, some or all of our net long-term capital gains and pay tax on such gains. In this case, we could elect for our stockholders to include their proportionate shares of such undistributed long-term capital gains in income, and to receive a corresponding credit for their share of the tax that we paid. Our stockholders would then increase the adjusted basis of their stock by the difference between (i) the amounts of capital gain dividends that we designated and that they include in their taxable income, and (ii) the tax that we paid on their behalf with respect to that income.

We have significant federal NOLs, which we may use to reduce the amount of distributions that we must make in order to comply with the REIT distribution requirements. Such losses, however, will generally not affect the tax treatment to our stockholders of any distributions that are actually made. See “—Taxation of Stockholders—Taxation of Taxable U.S. Stockholders—Distributions.”

If we fail to distribute during each calendar year at least the sum of (i) 85% of our ordinary income for such year, (ii) 95% of our capital gain net income for such year and (iii) any undistributed net taxable income from prior periods, we will be subject to a non-deductible 4% excise tax on the excess of such required distribution over the sum of (a) the amounts actually distributed, plus (b) the amounts of income we retained and on which we have paid corporate income tax.

We expect that, in the future, our REIT taxable income will be less than our cash flow because of our existing NOLs as well as depreciation and other non-cash charges included in computing REIT taxable income. Accordingly, we anticipate that we generally will have sufficient cash or liquid assets to enable us to satisfy the distribution requirements described above. However, from time to time, we may not have sufficient cash or other liquid assets to meet these distribution requirements due to timing differences between the actual receipt of income and payment of deductible expenses, and the inclusion of income and deduction of expenses in determining our taxable income. In addition, we may decide to retain our cash, rather than distribute it, in order to repay debt, acquire assets, or for other reasons. If these timing differences occur, we may borrow funds to pay dividends or pay dividends through the distribution of other property (including shares of our stock) in order to meet the distribution requirements, while preserving our cash.

If our taxable income for a particular year is subsequently determined to have been understated, we may be able to rectify a resultant failure to meet the distribution requirements for a year by paying “deficiency

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dividends” to stockholders in a later year, which may be included in our deduction for dividends paid for the earlier year. In this case, we may be able to avoid losing REIT qualification or being taxed on amounts distributed as deficiency dividends, subject to the 4% excise tax described above. We will be required to pay interest based on the amount of any deduction taken for deficiency dividends.

For purposes of the 90% distribution requirement and excise tax described above, any dividend that we declare in October, November or December of any year and that is payable to a stockholder of record on a specified date in any such month will be treated as both paid by us and received by the stockholder on December 31 of such year, provided that we actually pay the dividend before the end of January of the following calendar year.

Prohibited Transactions

Net income that we derive from a prohibited transaction is subject to a 100% tax. The term “prohibited transaction” generally includes a sale or other disposition of property (other than foreclosure property, as discussed below) that is held as inventory or primarily for sale to customers in the ordinary course of a trade or business. We intend to conduct our operations so that no asset that we own (or are treated as owning) will be treated as, or as having been, held as inventory or for sale to customers, and that a sale of any such asset will not be treated as having been in the ordinary course of our business. Whether property is held as inventory or “primarily for sale to customers in the ordinary course of a trade or business” depends on the particular facts and circumstances. No assurance can be given that any property that we sell will not be treated as inventory or property held for sale to customers, or that we can comply with certain safe-harbor provisions of the Code that would prevent such treatment. The 100% tax does not apply to gains from the sale of property that is held through a TRS or other taxable corporation, although such income will be subject to tax in the hands of the corporation at regular corporate rates. We intend to structure our activities to avoid prohibited transaction characterization.

Like-Kind Exchanges

We may dispose of properties in transactions intended to qualify as like-kind exchanges under the Code. Such like-kind exchanges are intended to result in the deferral of gain for U.S. federal income tax purposes. The failure of any such transaction to qualify as a like-kind exchange could require us to pay federal income tax, possibly including the 100% prohibited transaction tax, depending on the facts and circumstances surrounding the particular transaction.

Derivatives and Hedging Transactions

We may enter into hedging transactions with respect to interest rate exposure on one or more of our assets or liabilities. Any such hedging transactions could take a variety of forms, including the use of derivative instruments such as interest rate swap contracts, interest rate cap or floor contracts, futures or forward contracts, and options. Except to the extent provided by Treasury regulations, any income from a hedging transaction (including gain from the sale, disposition or termination of a position in such a transaction) will not constitute gross income for purposes of the 75% or 95% gross income test if we properly identify the transaction as specified in applicable Treasury regulations and we enter into such transaction (i) in the normal course of our business primarily to manage risk of interest rate changes or currency fluctuations with respect to borrowings made or to be made, or ordinary obligations incurred or to be incurred, to acquire or carry real estate assets; (ii) primarily to manage risk of currency fluctuations with respect to any item of income or gain that would be qualifying income under the 75% or 95% income tests; or (iii) in connection with the extinguishment of indebtedness with respect to which we have entered into a qualified hedging position described in clause (i) or the disposition of property with respect to which we have entered into a qualified hedging position described in clause (ii), primarily to manage the risks of such hedging positions. To the extent that we enter into other types of hedging transactions, the income from those transactions is likely to be treated as non-qualifying income for purposes of both of the 75% and 95% gross income tests. Moreover, to the extent that a position in a hedging transaction has positive value at any particular point in time, it may be treated as an asset that does not qualify for

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purposes of the REIT asset tests. We intend to structure any hedging transactions in a manner that does not jeopardize our qualification as a REIT. We may conduct some or all of our hedging activities (including hedging activities relating to currency risk) through a TRS or other corporate entity, the income from which may be subject to U.S. federal income tax, rather than by participating in the arrangements directly or through pass-through subsidiaries. No assurance can be given, however, that our hedging activities will not give rise to income or assets that do not qualify for purposes of the REIT tests, or that our hedging activities will not adversely affect our ability to satisfy the REIT qualification requirements.

Foreclosure Property

Foreclosure property is real property and any personal property incident to such real property (i) that we acquire as the result of having bid in the property at foreclosure, or having otherwise reduced the property to ownership or possession by agreement or process of law, after a default (or upon imminent default) on a lease of the property or a mortgage loan held by us and secured by the property, (ii) for which we acquired the related loan or lease at a time when default was not imminent or anticipated and (iii) with respect to which we made a proper election to treat the property as foreclosure property. We generally will be subject to tax at the maximum corporate rate (currently 21%) on any net income from foreclosure property, including any gain from the disposition of the foreclosure property, other than income that would otherwise be qualifying income for purposes of the 75% gross income test. Any gain from the sale of property for which a foreclosure property election has been made will not be subject to the 100% tax on gains from prohibited transactions described above, even if the property would otherwise constitute inventory or dealer property. We do not anticipate receiving any income from foreclosure property that does not qualify for purposes of the 75% gross income test.

Penalty Tax

Any redetermined rents, redetermined deductions, excess interest, or redetermined TRS service income that we or our TRSs generate will be subject to a 100% penalty tax. In general, redetermined rents are rents from real property that are overstated as a result of any services furnished to any of our tenants by a TRS, redetermined deductions and excess interest represent any amounts that are deducted by a TRS for amounts paid to us that are in excess of the amounts that would have been deducted based on arm’s length negotiations, and redetermined TRS service income is income of a TRS attributable to services provided to, or on behalf of, us (other than services furnished or rendered to a tenant of ours) to the extent that such income is lower than the income the TRS would have earned based on arm’s length negotiations. Rents that we receive will not constitute redetermined rents if they qualify for certain safe harbor provisions contained in the Code.

From time to time, our TRS may provide services to our tenants. We intend to set the fees paid to our TRS for such services at arm’s length rates, although the fees paid may not satisfy the safe-harbor provisions described above. These determinations are inherently factual, and the IRS has broad discretion to assert that amounts paid between related parties should be reallocated to clearly reflect their respective incomes. If the IRS successfully made such an assertion, we would be required to pay a 100% penalty tax on the excess of an arm’s length fee for tenant services over the amount actually paid.

Failure to Qualify

If we fail to satisfy one or more requirements for REIT qualification other than the income or asset tests, we could avoid disqualification as a REIT if our failure is due to reasonable cause and not to willful neglect and we pay a penalty of $50,000 for each such failure. Relief provisions are also available for failures of the income tests and asset tests, as described above in “—Income Tests” and “—Asset Tests.”

If we fail to qualify for taxation as a REIT in any taxable year, and the relief provisions described above do not apply, we would be subject to tax on our taxable income at regular corporate rates. We cannot deduct distributions to stockholders in any year in which we are not a REIT, nor would we be required to make distributions in such a year. In this situation, to the extent of current and accumulated earnings and profits, distributions to stockholders would be taxable as regular corporate dividends. Such dividends paid to U.S.

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stockholders that are individuals, trusts and estates may be taxable at the preferential income tax rates (i.e., the 20% maximum U.S. federal rate) for qualified dividends. In addition, subject to the limitations of the Code, corporate distributees may be eligible for the dividends received deduction. Unless we are entitled to relief under specific statutory provisions, we would also be disqualified from re-electing to be taxed as a REIT for the four taxable years following the year during which we lost our qualification. It is not possible to state whether, in all circumstances, we would be entitled to this statutory relief.

Taxation of Stockholders

Taxation of U.S. Stockholders

The following is a summary of certain U.S. federal income tax consequences of the ownership and disposition of our common stock applicable to taxable U.S. stockholders.

Distributions. So long as we qualify as a REIT, the distributions that we make to our taxable U.S. stockholders out of current or accumulated earnings and profits that we do not designate as capital gain dividends will generally be taken into account by such stockholders as ordinary income and will not be eligible for the dividends received deduction for corporations. With limited exceptions, our dividends are not eligible for taxation at the preferential income tax rates (i.e., the 20% maximum U.S. federal rate) for qualified dividends received by most U.S. stockholders that are individuals, trusts and estates from taxable C corporations. Such stockholders, however, are taxed at the preferential rates on dividends designated by and received from REITs to the extent that the dividends are attributable to:

• income retained by the REIT in the prior taxable year on which the REIT was subject to corporate level income tax (less the amount of tax);

• dividends received by the REIT from TRSs or other taxable C corporations;

• income in the prior taxable year from the sales of “built-in gain” property acquired by the REIT from C corporations in carryover basis transactions (less the amount of corporate tax on such income); or

• distributions of accumulated earnings and profits of C corporations acquired by the REIT.

In addition, under the recently enacted Tax Reform Act, qualified REIT dividends (within the meaning of Section 199A(e)(3) of the Code) constitute a part of a non-corporate taxpayer’s “qualified business income amount” and thus our non-corporate U.S. stockholders may be eligible to take a qualified business income deduction in an amount equal to 20% of such dividends received from us. Without further legislative action, the 20% deduction applicable to qualified REIT dividends will expire on January 1, 2026.

Distributions that we designate as capital gain dividends will generally be taxed to our U.S. stockholders as long-term capital gains, to the extent that such distributions do not exceed our actual net capital gain for the taxable year, without regard to the period for which the stockholder that receives such distribution has held its stock. We may elect to retain and pay taxes on some or all of our net long-term capital gains, in which case we may elect to apply provisions of the Code, which treat our U.S. stockholders as having received, solely for tax purposes, our undistributed capital gains, and the stockholders as receiving a corresponding credit for taxes that we paid on such undistributed capital gains. See “—Taxation of Crown Castle—Annual Distribution Requirements.” Corporate stockholders may be required to treat up to 20% of some capital gain dividends as ordinary income. Long-term capital gains are generally taxable at maximum U.S. federal rates of 20% in the case of U.S. stockholders that are individuals, trusts and estates, and 21% in the case of U.S. stockholders that are corporations. Capital gains attributable to the sale of depreciable real property held for more than 12 months are subject to a 25% maximum U.S. federal income tax rate for taxpayers who are taxed as individuals, to the extent of previously claimed depreciation deductions.

Distributions in excess of our current and accumulated earnings and profits will generally represent a return of capital and will not be taxable to a stockholder to the extent that the amount of such distributions does not

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exceed the adjusted basis of the stockholder’s shares in respect of which the distributions were made. Rather, the distribution will reduce the adjusted basis of the stockholder’s shares. To the extent that such distributions exceed the adjusted basis of a stockholder’s shares, the stockholder generally must include such distributions in income as long-term capital gain if the shares have been held for more than one year, or short-term capital gain if the shares have been held for one year or less. In addition, any dividend that we declare in October, November or December of any year and that is payable to a stockholder of record on a specified date in any such month will be treated as both paid by us and received by the stockholder on December 31 of such year, provided that we actually pay the dividend before the end of January of the following calendar year.

To the extent that we have available net operating losses and capital losses carried forward from prior tax years, such losses may reduce the amount of distributions that we must make in order to comply with the REIT distribution requirements. See “—Taxation of Crown Castle—Annual Distribution Requirements.” Such losses, however, are not passed through to stockholders and do not offset income of stockholders from other sources, nor would such losses affect the character of any distributions that we make, which are generally subject to tax in the hands of stockholders to the extent that we have current or accumulated earnings and profits.

Dispositions of Our Common Stock. If a U.S. stockholder sells or disposes of shares of our common stock, it will generally recognize gain or loss for U.S. federal income tax purposes in an amount equal to the difference between (i) the amount of cash and the fair market value of any property received on the sale or other disposition and (ii) the stockholder’s adjusted tax basis in the shares of common stock. In general, capital gains recognized by individuals, trusts and estates upon the sale or disposition of our common stock will be subject to a maximum U.S. federal income tax rate of 20% if the stock is held for more than one year, and will be taxed at ordinary income rates (of up to 37%) if the stock is held for one year or less. Gains recognized by stockholders that are corporations are subject to U.S. federal income tax at a maximum rate of 21%, whether or not such gains are classified as long-term capital gains. Capital losses recognized by a stockholder upon the disposition of our common stock that was held for more than one year at the time of disposition will be considered long-term capital losses, and are generally available only to offset capital gain income of the stockholder but not ordinary income (except in the case of individuals, who may also offset up to $3,000 of ordinary income each year). In addition, any loss upon a sale or exchange of shares of our common stock by a stockholder who has held the shares for six months or less, after applying holding period rules, will be treated as a long-term capital loss to the extent of actual or deemed distributions that we make that are required to be treated by the stockholder as long-term capital gain.

If an investor recognizes a loss upon a subsequent disposition of our common stock or other securities in an amount that exceeds a prescribed threshold, it is possible that the provisions of Treasury regulations involving “reportable transactions” could apply, with a resulting requirement to separately disclose the loss-generating transaction to the IRS. These regulations, though directed towards “tax shelters,” are broadly written and apply to transactions that would not typically be considered tax shelters. The Code imposes significant penalties for failure to comply with these requirements. You should consult your tax advisor concerning any possible disclosure obligation with respect to the receipt or disposition of our common stock or securities or transactions that we might undertake directly or indirectly. Moreover, you should be aware that we and other participants in the transactions in which we are involved (including their advisors) might be subject to disclosure or other requirements pursuant to these regulations.

Passive Activity Losses and Investment Interest Limitations. Distributions that we make and gains arising from the sale or exchange by a U.S. stockholder of our common stock will not be treated as passive activity income. As a result, stockholders will not be able to apply any “passive losses” against income or gain relating to our common stock. To the extent that distributions we make do not constitute a return of capital, they will be treated as investment income for purposes of computing the investment interest limitation.

Medicare 3.8% Tax on Investment Income. Certain U.S. stockholders who are individuals, estates or trusts and whose income exceeds certain thresholds are required to pay a 3.8% Medicare tax on dividends and certain other investment income, including capital gains from the sale or other disposition of our common stock.

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Taxation of Non-U.S. Stockholders

The following is a summary of certain U.S. federal income and estate tax consequences of the ownership and disposition of our common stock applicable to non-U.S. stockholders.

Ordinary Dividends. The portion of dividends received by non-U.S. stockholders that (i) is payable out of our earnings and profits, (ii) is not attributable to capital gains that we recognize and (iii) is not effectively connected with a U.S. trade or business of the non-U.S. stockholder, will be subject to U.S. withholding tax at the rate of 30%, unless reduced or eliminated by treaty.

In general, non-U.S. stockholders will not be considered to be engaged in a U.S. trade or business solely as a result of their ownership of our common stock. In cases where the dividend income from a non-U.S. stockholder’s investment in our common stock is, or is treated as, effectively connected with the non-U.S. stockholder’s conduct of a U.S. trade or business, the non-U.S. stockholder generally will be subject to U.S. federal income tax at graduated rates, in the same manner as U.S. stockholders are taxed with respect to such dividends. Such effectively connected income must generally be reported on a U.S. income tax return filed by or on behalf of the non-U.S. stockholder. The income may also be subject to a branch profits tax at the rate of 30% (unless reduced or eliminated by treaty) in the case of a non-U.S. stockholder that is a corporation.

Non-Dividend Distributions. Unless our common stock constitutes a U.S. real property interest (“USRPI”), distributions that we make which are not dividends out of our earnings and profits will generally not be subject to U.S. income tax. If we cannot determine at the time a distribution is made whether or not the distribution will exceed current and accumulated earnings and profits, the distribution will be subject to withholding at the rate applicable to dividends. The non-U.S. stockholder may seek a refund from the IRS of any amounts withheld if it is subsequently determined that the distribution was, in fact, in excess of our current and accumulated earnings and profits. If our common stock constitutes a USRPI, as described below, distributions that we make in excess of the sum of (i) the stockholder’s proportionate share of our earnings and profits, plus (ii) the stockholder’s basis in its common stock, will, except as described below, be taxed under the Foreign Investment in Real Property Tax Act of 1980 (“FIRPTA”), at the rate of tax, including any applicable capital gains rates, that would apply to a U.S. stockholder of the same type (e.g., an individual or a corporation, as the case may be), and the collection of the tax may be enforced by a withholding at a rate of 15% of the amount by which the distribution exceeds the stockholder’s share of our earnings and profits.

Capital Gain Dividends. Under FIRPTA, a distribution that we make to a non-U.S. stockholder, to the extent attributable to gains from dispositions of USRPIs that we held directly or through pass-through subsidiaries, or USRPI capital gains, will, except as described below, be considered effectively connected with a U.S. trade or business of the non-U.S. stockholder and will be subject to U.S. income tax at the rates applicable to U.S. individuals or corporations, without regard to whether we designate the distribution as a capital gain dividend. See above under “—Ordinary Dividends,” for a discussion of the consequences of income that is effectively connected with a U.S. trade or business. In addition, we will be required to withhold tax equal to 21% of the maximum amount that could have been designated as USRPI capital gains dividends. Distributions subject to FIRPTA may also be subject to a branch profits tax at the rate of 30% (unless reduced or eliminated by treaty) in the hands of a non-U.S. stockholder that is a corporation. A distribution is not attributable to USRPI capital gain if we held an interest in the underlying asset solely as a creditor. Capital gain dividends received by a non-U.S. stockholder that are attributable to dispositions of our assets other than USRPIs are not subject to U.S. federal income or withholding tax, unless (i) the gain is effectively connected with the non-U.S. stockholder’s U.S. trade or business, in which case the non-U.S. stockholder would be subject to the same treatment as U.S. stockholders with respect to such gain, except that a non-U.S. stockholder that is a corporation may also be subject to a branch profits tax at the rate of 30% (unless reduced or eliminated by treaty), or (ii) the non-U.S. stockholder is a nonresident alien individual who was present in the United States for 183 days or more during the taxable year and has a “tax home” in the United States, in which case the non-U.S. stockholder will incur a 30% tax on his capital gains. A significant portion of our assets are USRPIs.

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A capital gain dividend that would otherwise have been treated as a USRPI capital gain will not be so treated or be subject to FIRPTA, and generally will not be treated as income that is effectively connected with a U.S. trade or business, and instead will be treated in the same manner as an ordinary dividend (see “—Ordinary Dividends”), if (i) the capital gain dividend is received with respect to a class of stock that is regularly traded on an established securities market located in the United States and (ii) the recipient non-U.S. stockholder does not own more than 10% of that class of stock at any time during the year ending on the date on which the capital gain dividend is received. Our common stock is currently, and we anticipate that it will continue to be, “regularly traded” on an established securities market.

Dispositions of Our Common Stock. Unless our common stock constitutes a USRPI, a sale of our common stock by a non-U.S. stockholder generally will not be subject to U.S. taxation under FIRPTA. Subject to certain exceptions discussed below, our common stock will be treated as a USRPI if 50% or more of our assets throughout a prescribed testing period consist of interests in real property located within the United States, excluding, for this purpose, interests in real property solely in a capacity as a creditor. We expect that 50% or more of our assets will consist of USRPIs.

Even if the foregoing 50% test is met, however, our common stock will not constitute a USRPI if we are a “domestically controlled qualified investment entity.” A domestically controlled qualified investment entity includes a REIT, less than 50% of the value of which is held, directly or indirectly, by non-U.S. stockholders at all times during a specified testing period (after applying certain presumptions regarding the ownership of our stock, as described in the Code). As described above in “Description of Capital Stock—Ownership Limitations and Transfer Restrictions,” we have implemented restrictions designed to protect our status as a “domestically controlled qualified investment entity,” and we believe that we are and will continue to be a domestically controlled qualified investment entity, and that a sale of our common stock should not be subject to taxation under FIRPTA. However, no assurance can be given that we are or will remain a domestically controlled qualified investment entity.

In the event that we are not a domestically controlled qualified investment entity, but our stock is “regularly traded,” as defined by applicable Treasury regulations, on an established securities market, a non-U.S. stockholder’s sale of our common stock nonetheless also would not be subject to tax under FIRPTA as a sale of a USRPI, provided that the selling non-U.S. stockholder held 10% or less of our outstanding shares of common stock any time during a prescribed testing period. We believe that our common stock is and will continue to be regularly traded on an established securities market.

If gain on the sale of our common stock were subject to taxation under FIRPTA, the non-U.S. stockholder would be required to file a U.S. federal income tax return and would be subject to the same treatment as a U.S. stockholder with respect to such gain, subject to applicable alternative minimum tax and a special alternative minimum tax in the case of non-resident alien individuals. Moreover, in order to enforce the collection of the tax, the purchaser of the common stock could be required to withhold 15% of the purchase price and remit such amount to the IRS.

Gain from the sale of our common stock that would not otherwise be subject to FIRPTA will nonetheless be taxable in the United States to a non-U.S. stockholder in two cases: (i) if the non-U.S. stockholder’s investment in our common stock is effectively connected with a U.S. trade or business conducted by such non-U.S. stockholder, the non-U.S. stockholder will be subject to the same treatment as a U.S. stockholder with respect to such gain, except that a non-U.S. stockholder that is a corporation may also be subject to a branch profits tax at a rate of 30% (unless reduced or eliminated by treaty), or (ii) if the non-U.S. stockholder is a nonresident alien individual who was present in the United States for 183 days or more during the taxable year and has a “tax home” in the United States, the nonresident alien individual will be subject to a 30% tax on the individual’s capital gain. In addition, even if we are a domestically controlled qualified investment entity, upon disposition of our common stock (subject to the 10% exception applicable to “regularly traded” stock described above), a non-U.S. stockholder may be treated as having gain from the sale or exchange of a USRPI if the non-U.S.

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stockholder (a) disposes of our common stock within a 30-day period preceding the ex-dividend date of a distribution, any portion of which, but for the disposition, would have been treated as gain from the sale or exchange of a USRPI and (b) acquires, or enters into a contract or option to acquire, other shares of our common stock within 30 days after such ex-dividend date.

Special FIRPTA Rules. Amendments to FIRPTA enacted in the Omnibus Appropriations Act created certain exemptions from FIRPTA and otherwise modified the application of the foregoing FIRPTA rules for particular types of non-U.S. investors, including “qualified foreign pension funds” and their wholly owned foreign subsidiaries and certain widely held, publicly traded “qualified collective investment vehicles.” Non-U.S. stockholders are urged to consult their tax advisors regarding the applicability of these or any other special FIRPTA rules to their particular investment in our common stock.

Estate tax. If our common stock is owned or treated as owned by an individual who is not a citizen or resident (as specially defined for U.S. federal estate tax purposes) of the United States at the time of such individual’s death, the stock will be includable in the individual’s gross estate for U.S. federal estate tax purposes, unless an applicable estate tax treaty provides otherwise, and may therefore be subject to U.S. federal estate tax.

Non-U.S. stockholders are urged to consult their tax advisors regarding the U.S. federal, state, local and foreign income and other tax consequences of owning our common stock.

Taxation of Tax-Exempt Stockholders

The following is a summary of certain U.S. federal income tax consequences of the ownership and disposition of our common stock applicable to tax-exempt stockholders.

Tax-exempt entities, including qualified employee pension and profit sharing trusts and individual retirement accounts, generally are exempt from U.S. federal income taxation. However, they may be subject to taxation on their unrelated business taxable income (“UBTI”). While some investments in real estate may generate UBTI, the IRS has ruled that dividend distributions from a REIT to a tax-exempt entity do not constitute UBTI. Based on that ruling, and provided that (i) a tax-exempt stockholder has not held our common stock as “debt financed property” within the meaning of the Code (i.e., where the acquisition or holding of the property is financed through a borrowing by the tax-exempt stockholder) and (ii) our common stock is not otherwise used in an unrelated trade or business, distributions that we make and income from the sale of our common stock generally should not give rise to UBTI to a tax-exempt stockholder.

Tax-exempt stockholders that are social clubs, voluntary employee benefit associations, supplemental unemployment benefit trusts, and qualified group legal services plans exempt from U.S. federal income taxation under sections 501(c)(7), (c)(9), (c)(17) and (c)(20) of the Code are subject to different UBTI rules, which generally require such stockholders to characterize distributions that we make as UBTI.

In certain circumstances, a pension trust that owns more than 10% of our stock could be required to treat a percentage of any dividends received from us as UBTI if we are a “pension-held REIT.” We will not be a pension-held REIT unless (i) we are required to “look through” one or more of our pension trust stockholders in order to satisfy the REIT “closely-held” test and (ii) either (a) one pension trust owns more than 25% of the value of our stock or (b) one or more pension trusts, each individually holding more than 10% of the value of our stock, collectively own more than 50% of the value of our stock. Certain restrictions on ownership and transfer of our stock generally should prevent a tax-exempt entity from owning more than 10% of the value of our stock and generally should prevent us from becoming a pension-held REIT.

Tax-exempt stockholders are urged to consult their tax advisors regarding the U.S. federal, state, local and foreign income and other tax consequences of owning our common stock.

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Legislative or Other Actions Affecting REITs

The present U.S. federal income tax treatment of REITs may be modified, possibly with retroactive effect, by legislative, judicial or administrative action at any time. The REIT rules are constantly under review by persons involved in the legislative process and by the IRS and the Treasury which may result in statutory changes as well as revisions to regulations and interpretations. Changes to the U.S. federal tax laws and interpretations thereof could adversely affect an investment in our common stock.

Other Tax Considerations

Foreign Account Tax Compliance Act

Legislation enacted in 2010 and existing guidance issued thereunder requires withholding at a rate of 30% on dividends in respect of, and, after December 31, 2018, gross proceeds from the sale of, our common stock held by or through certain foreign financial institutions (including investment funds), unless such institution enters into an agreement with the Treasury to report, on an annual basis, information with respect to shares in the institution held by certain U.S. persons and by certain non-U.S. entities that are wholly or partially owned by U.S. persons and to withhold on certain payments. Accordingly, the entity through which our common stock is held will affect the determination of whether such withholding is required. Similarly, dividends in respect of, and, after December 31, 2018, gross proceeds from the sale of, our common stock held by an investor that is a non-financial non-U.S. entity which does not qualify under certain exemptions will be subject to withholding at a rate of 30%, unless such entity either (i) certifies to us that such entity does not have any “substantial United States owners” or (ii) provides certain information regarding the entity’s “substantial United States owners,” which we or the applicable withholding agent will in turn provide to the Secretary of the Treasury. An intergovernmental agreement between the United States and an applicable foreign country, or future Treasury regulations or other guidance may modify these requirements. We will not pay any additional amounts to stockholders in respect of any amounts withheld. Non-U.S. stockholders are urged to consult their tax advisors regarding the possible implications of the legislation on their investment in our common stock.

State, Local and Foreign Taxes

We and our subsidiaries and stockholders may be subject to state, local or foreign taxation in various jurisdictions including those in which we or they transact business, own property or reside. Our state, local or foreign tax treatment and that of our stockholders may not conform to the U.S. federal income tax treatment discussed above. Our foreign subsidiaries most likely will be subject to foreign income taxation. Any foreign taxes that we incur do not pass through to stockholders as a credit against their U.S. federal income tax liability. Prospective investors are urged to consult their tax advisors regarding the application and effect of state, local and foreign income and other tax laws on an investment in our common stock.

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PLAN OF DISTRIBUTION

We have entered into separate sales agreements with each of Merrill Lynch, Pierce, Fenner & Smith Incorporated, Barclays Capital Inc., Citigroup Global Markets Inc., Credit Agricole Securities (USA) Inc., Fifth Third Securities, Inc., Jefferies LLC, J.P. Morgan Securities LLC, Mizuho Securities USA LLC, Morgan Stanley & Co. LLC, MUFG Securities Americas Inc., RBC Capital Markets, LLC, SG Americas Securities, LLC, SMBC Nikko Securities America, Inc., SunTrust Robinson Humphrey, Inc., TD Securities (USA) LLC and Wells Fargo Securities, LLC, the Sales Agents, under which we may issue and sell shares of our common stock having an aggregate gross sales price of up to $750,000,000 from time to time through the Sales Agents, as our agents for the offer and sale of our common stock.

Sales of shares of our common stock to which this prospectus supplement and the accompanying prospectus relate, if any, will be made by means of ordinary brokers’ transactions on the NYSE or otherwise at market prices prevailing at the time of sale, at prices related to prevailing market prices or, subject to our specific instructions, at negotiated prices. As our agents, the Sales Agents will not engage in any transactions that stabilize our common stock.

Each Sales Agent will offer the shares of our common stock subject to the terms and conditions of the applicable sales agreement on a daily basis or as otherwise agreed between us and each Sales Agent. We will designate the maximum amount of shares of common stock to be sold through each Sales Agent and the minimum price per share at which each share of our common stock may be sold. Subject to the terms and conditions of the applicable sales agreement, each Sales Agent will use its commercially reasonable efforts to sell the shares offered as our agent. The Sales Agents may not sell common stock if the sales cannot be effected at or above the minimum price designated by us from time to time. We or any Sales Agent may suspend the offering of shares of common stock upon proper notice to the other party.

We will pay each Sales Agent a commission for its services in acting as agent in the sale of shares of our common stock that may be offered hereby. Each Sales Agent will receive from us a commission that will not exceed, but may be lower than, 2.00% of the gross sales price of the shares sold pursuant to the applicable sales agreement. The foregoing rate of compensation shall not apply when a Sales Agent acts as principal, in which case we may sell shares of our common stock to such Sales Agent as principal at a price agreed upon. The remaining proceeds, after deducting any expenses payable by us and any transaction fees imposed by any governmental, regulatory or self-regulatory organization in connection with the sales, will equal our net proceeds for the sale of such shares. Notwithstanding the foregoing, in the event we engage a Sales Agent for a sale of shares of our common stock that would constitute a “distribution” within the meaning of Rule 100 of Regulation M, we and such Sales Agent will use reasonable commercial efforts to agree to compensation that is customary for such Sales Agent with respect to such transactions. Each Sales Agent will provide written confirmation to us following the close of trading on the NYSE each day in which shares of common stock are sold by such Sales Agent for us under the applicable sales agreement. Each confirmation will include the number of shares sold on such day, the gross sales proceeds of such shares, the compensation payable by us to the applicable Sales Agent and the proceeds to us net of such compensation.

Settlement for sales of shares of our common stock will occur, unless we and the applicable Sales Agent agree otherwise, on the second business day (other than a day on which the NYSE is scheduled to close prior to its regular weekday closing time) following the trade date on which any sales are made in return for payment of the proceeds to us net of compensation paid by us to such Sales Agent. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

Under the terms of the sales agreements, we also may sell shares of our common stock to any Sales Agent as principal for its own account. If we sell shares to any Sales Agent as principal, we will enter into a separate terms agreement setting forth the terms of such transaction, and we will describe the agreement in a separate prospectus supplement or pricing supplement.

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Unless otherwise set forth in a prospectus supplement, we will report at least quarterly the number of shares of common stock sold through the Sales Agents under the sales agreements, the net proceeds to us, and the compensation paid by us to the Sales Agents in connection with the sales of our common stock.

Under each of the sales agreements, if a Sales Agent or we have reason to believe that the exemptive provisions set forth in Rule 101(c)(1) of Regulation M under the Exchange Act (applicable to actively-traded securities) are not satisfied with respect to us or our common stock, that party will promptly notify the other, and sales of common stock under the applicable sales agreement and terms agreement will be suspended until that or other exemptive provisions have been satisfied in the reasonable judgment of the Sales Agent and us.

In connection with the sale of common stock on our behalf, each Sales Agent may be deemed to be an “underwriter” within the meaning of the Securities Act and compensation of the Sales Agents may be deemed to be underwriting discounts or commissions. We have agreed to provide indemnification and contribution to the Sales Agents against certain liabilities, including liabilities under the Securities Act.

The offering of shares of common stock pursuant to the sales agreements will terminate upon the earlier of (i) the issuance and sale of shares of our common stock subject to the sales agreements having an aggregate gross sales price of $750,000,000 and (ii) with respect to a particular sales agreement, the termination of such sales agreement by us or by the applicable Sales Agent as permitted therein.

Because there is no minimum offering amount contemplated by the sales agreements, commissions and net proceeds to us, if any, are not determinable at this time. We have agreed to reimburse the Sales Agents for certain expenses in certain circumstances in connection with this offering. We estimate that the expenses of this offering payable by us, excluding compensation payable to the Sales Agents under the terms of the applicable sales agreement, will be approximately $700,000.

The Sales Agents and their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. In the ordinary course of business, the Sales Agents or their affiliates have provided and may in the future continue to provide investment banking, commercial banking, financial advisory and other financial services to us and our subsidiaries for which they have received and may in the future receive compensation. In that regard, certain of the Sales Agents or their affiliates are and may in the future be lenders under our senior unsecured credit facilities or holders of certain of our outstanding debt securities. Certain Sales Agents or their affiliates serve and may in the future serve other roles under our senior unsecured credit facilities or hold certain of our outstanding debt securities. Because we intend to use the net proceeds from any sales under this prospectus supplement for general corporate purposes, which may include (i) the funding of future acquisitions or investments or (ii) the repayment or repurchase of any outstanding indebtedness, including outstanding indebtedness under our senior unsecured credit facilities or debt securities, the Sales Agents or their affiliates who are, or who may in the future be, lenders under our senior unsecured credit facilities or holders of certain of our outstanding debt securities, may receive a pro rata portion of any net proceeds from the offering of shares of our common stock sold pursuant to the sales agreements to the extent we use any such proceeds to reduce amounts outstanding under our senior unsecured credit facilities or debt securities.

In addition, in the ordinary course of their various business activities, the Sales Agents and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers and such investment and securities activities may involve securities or instruments of ours or our subsidiaries. The Sales Agents and their respective affiliates may also make investment recommendations or publish or express independent research views in respect of our securities or financial instruments and may at any time hold, or recommend to clients that they acquire, long or short positions in such securities and instruments.

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LEGAL MATTERS

The validity of the shares of our common stock will be passed upon for us by Cravath, Swaine & Moore LLP, New York, New York. Skadden, Arps, Slate, Meagher & Flom LLP, Los Angeles, California, will act as counsel for the Sales Agents. Each of Cravath, Swaine & Moore LLP, New York, New York, and Skadden, Arps, Slate, Meagher & Flom LLP, Chicago, Illinois, has acted as Tax Counsel to us in connection with this offering.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control over Financial Reporting), incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2017, have been so incorporated in reliance on the report (which contains an explanatory paragraph on the effectiveness of internal control over financial reporting due to the exclusion of certain elements of the internal control over financial reporting of the FiberNet, Wilcon and Lightower businesses the registrant acquired during 2017) of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The financial statements of LTS Group Holdings LLC and its subsidiary as of and for the year ended December 31, 2016, incorporated in this prospectus supplement by reference to our Current Report on Form 8-K/A filed December 15, 2017 (which amended our Current Report on Form 8-K filed November 1, 2017), have been audited by Deloitte & Touche LLP, independent auditors, as stated in their report, which is incorporated herein by reference. Such financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

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WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the internet at the SEC’s website at http://www.sec.gov. You may also read and copy any document we file with the SEC at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room. Our SEC filings are also available through the investor relations section of our website at http://investor.crowncastle.com. Except for documents incorporated by reference into this prospectus supplement and the accompanying prospectus as described below, no information contained in, or that can be accessed through, our website is incorporated by reference into this prospectus supplement or the accompanying prospectus, and no such information should be considered as part of this prospectus supplement or the accompanying prospectus.

We are “incorporating by reference” into this prospectus supplement and the accompanying prospectus specific documents that we file with the SEC, which means that we can disclose important information to you by referring you to those documents that are considered part of this prospectus supplement and the accompanying prospectus. Information that we file subsequently with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below, and any future documents that we file with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act until the termination of the offering of the securities covered by this prospectus supplement (other than information furnished under Item 2.02 or 7.01 (including any related exhibit under Item 9.01) of any Form 8-K, which is not deemed filed under the Exchange Act). This prospectus supplement and the accompanying prospectus are part of a registration statement filed with the SEC.

We are “incorporating by reference” into this prospectus supplement and the accompanying prospectus the following documents filed with the SEC (excluding any portions of such documents that have been “furnished” but not “filed” for purposes of the Exchange Act):

• our Annual Report on Form 10-K for the fiscal year ended December 31, 2017;

• the portions of our Definitive Proxy Statement on Schedule 14A, filed April 2, 2018, that are incorporated by reference into our Annual Report on Form 10-K for the fiscal year ended December 31, 2017;

• our Current Reports on Form 8-K filed January 10, 2018, January 17, 2018, February 27, 2018, March 5, 2018 and March 26, 2018 and our Current Report on Form 8-K/A filed February 21, 2018 (which amended our Current Report on Form 8-K filed November 2, 2017);

• our Current Report on Form 8-K/A filed December 15, 2017 (which amended our Current Report on Form 8-K filed November 1, 2017); and

• the description of our capital stock contained in Exhibit 4.1 of our Current Report on Form 8-K filed December 16, 2014, as supplemented by the description of our Mandatory Convertible Preferred Stock contained in our Final Prospectus Supplement filed pursuant to Rule 424(b)(2) under the Securities Act on July 24, 2017 and any subsequent amendments and reports filed for the purpose of updating such descriptions (collectively, “Capital Stock Description”).

We will provide to each person, including any beneficial owner of shares of our capital stock, to whom a prospectus supplement is delivered, upon written or oral request and without charge, a copy of the documents referred to above that we have incorporated in this prospectus supplement and the accompanying prospectus by reference. You can request copies of such documents if you write or call us at the following address or telephone number: Investor Relations, Crown Castle International Corp., 1220 Augusta Drive, Suite 600, Houston, Texas 77057, (713) 570-3000, or you may visit the investor relations section of our website at http://investor.crowncastle.com for copies of any such document. Except as expressly stated herein, no information contained in, or that can be accessed through, our website is incorporated by reference into this prospectus supplement or the accompanying prospectus, and no such information should be considered a part of this prospectus supplement or the accompanying prospectus.

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This prospectus supplement, the accompanying prospectus or information incorporated by reference herein or therein contains summaries of certain agreements that we have filed as exhibits to various SEC filings, as well as certain agreements that we will enter into in connection with the offering of securities covered by any particular prospectus supplement. The descriptions of these agreements contained in this prospectus supplement, the accompanying prospectus or information incorporated by reference herein or therein do not purport to be complete and are subject to, and qualified in their entirety by reference to, the definitive agreements. Copies of the definitive agreements will be made available without charge to you by making a written or oral request to us.

Any statement contained herein or in a document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained herein, in any other subsequently filed document which also is or is deemed to be incorporated by reference herein or in the accompanying prospectus, modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified and superseded, to constitute a part of this prospectus supplement.

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PROSPECTUS

CROWN CASTLE INTERNATIONAL CORP.

Debt Securities

Preferred Stock

Common Stock

Warrants

The securities covered by this prospectus may be sold from time to time by Crown Castle International Corp. In addition, selling security holders to be named in a prospectus supplement may offer and sell from time to time securities in such amounts as are set forth in such prospectus supplement. We may, and any selling security holder may, offer the securities independently or together in any combination for sale to or through underwriters, dealers or agents as designated from time to time, or directly to one or more other purchasers or through a combination of such methods. Unless otherwise set forth in a prospectus supplement, we will not receive any proceeds from the sale of securities by any selling security holder.

When we offer securities, we will provide you with a prospectus supplement describing the specific terms of the specific issue of securities, including the offering price of the securities. You should carefully read this prospectus, the applicable prospectus supplement and any free writing prospectus relating to the specific issue of securities, together with the documents we incorporate by reference herein and therein, before you decide to invest in any of these securities.

Our common stock is traded on the New York Stock Exchange (“NYSE”) under the symbol “CCI.”

The securities may be offered and sold to or through underwriters, dealers or agents as designated from time to time, or directly to one or more other purchasers or through a combination of such methods. See “Plan of Distribution” on page 29. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names, and any applicable purchase price, fee, commission or discount arrangements between or among them, will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement.

Investing in our securities involves a high degree of risk. See “Risk Factors” on page 3 of this prospectus. You should carefully review the risks and uncertainties described under the heading “Risk Factors” contained in the applicable prospectus supplement and any related free writing prospectus, and under similar headings in the documents that are incorporated by reference into this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is March 26, 2018.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS		1
THE COMPANY		2
RISK FACTORS		3
CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS		4
SELLING SECURITY HOLDERS		5
USE OF PROCEEDS		6
RATIO OF EARNINGS TO FIXED CHARGES AND EARNINGS TO COMBINED FIXED CHARGES AND DIVIDENDS ON PREFERRED STOCK AND LOSSES ON PURCHASES OF PREFERRED STOCK		7
DESCRIPTION OF DEBT SECURITIES		8
DESCRIPTION OF CAPITAL STOCK		20
DESCRIPTION OF WARRANTS		28
PLAN OF DISTRIBUTION		29
LEGAL MATTERS		31
EXPERTS		32
WHERE YOU CAN FIND MORE INFORMATION		32

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement on Form S-3 that we filed with the U.S. Securities and Exchange Commission (“SEC”) using the “shelf” registration process. Under the shelf registration process, we, or certain of our security holders, may from time to time sell the securities described in this prospectus in one or more offerings.

This prospectus provides you with a general description of the securities that we or a selling security holder may offer. Each time we, or, under certain circumstances, our security holders, sell securities in a manner not described herein, we will provide you with a prospectus supplement containing specific information about the terms of the offering and the means of distribution. A prospectus supplement may include other special considerations applicable to such offering of securities. The prospectus supplement may also add, update or change information in this prospectus. If there is any inconsistency between the information in this prospectus and any prospectus supplement, you should rely on the information in the prospectus supplement. You should carefully read this prospectus, the applicable prospectus supplement and any free writing prospectus relating to the specific issue of securities, together with the additional information described under the heading “Where You Can Find More Information,” before you decide to invest in any of these securities.

The prospectus supplement will describe: the terms of the securities offered, any initial public offering price, the price paid to us for the securities, the net proceeds to us, the manner of distribution and any underwriting compensation and the other specific material terms related to the offering of the applicable securities. For more detail on the terms of the securities, you should read the exhibits filed with or incorporated by reference in our registration statement of which this prospectus forms a part.

In this prospectus, unless otherwise indicated or the context otherwise requires, the terms “Crown Castle,” “we,” “our,” “Company” and “us” refer to Crown Castle International Corp., a Delaware corporation, and its subsidiaries on a consolidated basis. Additionally, unless the context suggests otherwise, references to “U.S.” are to the United States of America and Puerto Rico, collectively.

References to “securities” include any security that we or our security holders might sell under this prospectus or any prospectus supplement.

We prepare our financial statements, including all of the financial statements incorporated by reference in this prospectus, in U.S. dollars and in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”). Our fiscal year ends on December 31. In this prospectus, except where otherwise indicated, references to “$” or “dollars” are to the lawful currency of the United States.

This prospectus contains summaries of certain provisions contained in some of the documents described herein. Please refer to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of the documents referred to herein have been filed, or will be filed or incorporated by reference as exhibits to the registration statement of which this prospectus forms a part, and you may obtain copies of those documents as described under the heading “Where You Can Find More Information.”

You should rely only on the information contained in this prospectus, any prospectus supplement and any free writing prospectus, together with the documents we incorporate by reference herein or therein. We have not authorized anyone to provide you with different information. The distribution of this prospectus and the sale of these securities in certain jurisdictions may be restricted by law. Persons in possession of this prospectus are required to inform themselves about and observe any such restrictions. We are not making an offer to sell these securities in any jurisdiction where such offer or sale is not permitted. You should assume that the information appearing or incorporated by reference in this prospectus, any prospectus supplement or any free writing prospectus is accurate only as of the date on the front cover of this prospectus, the date of the applicable prospectus supplement, the date of the applicable free writing prospectus or the date of such incorporated document, as the case may be. Our business, financial condition, results of operations and prospects may have changed since the applicable date.

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THE COMPANY

We own, operate and lease shared communications infrastructure that is geographically dispersed throughout the U.S., including (1) approximately 40,000 towers and other structures, such as rooftops (collectively, “towers”) and (2) approximately 60,000 route miles of fiber primarily supporting small cell networks (“small cells”) and fiber solutions. Our towers, fiber and small cells assets are collectively referred to herein as “communications infrastructure,” and our customers on our communications infrastructure are referred to herein as “tenants.” Our customers include AT&T, T-Mobile, Verizon Wireless and Sprint, which collectively accounted for 83% of our site rental revenues for the year ended December 31, 2017.

Our core business is providing access, including space or capacity, to our shared communications infrastructure via long-term contracts in various forms, including lease, license, sublease and service agreements. We seek to increase our site rental revenues by adding more tenants on our shared communications infrastructure, which we expect to result in significant incremental cash flows due to our low incremental operating costs. Site rental revenues represented 84% of our consolidated net revenues for the year ended December 31, 2017.

As of December 31, 2017, approximately 56% and 71% of our towers were located in the 50 and 100 largest U.S. basic trading areas (“BTAs”), respectively. Our towers have a significant presence in each of the top 100 BTAs. As of December 31, 2017, we derive in excess of one-third of our Towers segment site rental gross margin on land and other property interests (collectively, “land”) that we own, including fee interests and perpetual easements, and we derive approximately two-thirds of our Towers segment site rental gross margin from land that we lease, sublease, manage or license.

The majority of our small cells and fiber are located in major metropolitan areas, including a presence within every major U.S. market. The vast majority of our fiber assets are located on public rights-of-way.

As part of our effort to provide comprehensive communications infrastructure solutions, we also offer certain network services primarily relating to our towers and small cells, predominately consisting of (1) site development services relating to existing or new tenant equipment installations, including: site acquisition, architectural and engineering, or zoning and permitting and (2) tenant equipment installation or subsequent augmentations. The large majority of our network services and other revenues relate to our Towers segment.

Our principal executive offices are located at 1220 Augusta Drive, Suite 600, Houston, Texas 77057, and our telephone number is (713) 570-3000. We maintain an internet website at www.crowncastle.com. Except as expressly stated herein, no information contained in, or that can be accessed through, our website is incorporated by reference into this prospectus, and no such information should be considered a part of this prospectus.

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RISK FACTORS

Investing in our securities involves risks. Potential investors are urged to read and consider the risk factors and other disclosures relating to an investment in securities issued by Crown Castle described in our Annual Report on Form 10-K for the fiscal year ended December 31, 2017, as updated by annual, quarterly and other reports and documents we file with the SEC after the date of this prospectus and that are incorporated by reference herein. Before making an investment decision with respect to an offering of our securities, you should carefully consider those risks as well as other information we include or incorporate by reference in this prospectus, the applicable prospectus supplement and any free writing prospectus relating to the specific issue of securities. If any of the events or developments described actually occurred, our business, financial condition or results of operations would likely suffer. The risks and uncertainties we have described are not the only ones facing the Company. Additional risks and uncertainties not presently known to us or that we currently consider immaterial may also affect our business operations. To the extent a particular offering implicates additional risks, we will include a discussion of those risks in the applicable prospectus supplement.

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CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS

The statements contained in or incorporated by reference in this prospectus include certain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, with respect to the financial condition, results of operations, business strategies, operating efficiencies or synergies, competitive positions, growth opportunities for existing products, plans and objectives of management, markets for our securities and other matters that are based on our management’s expectations as of the filing date of this prospectus with the SEC. Statements contained in or incorporated by reference in this prospectus that are not historical facts are hereby identified as “forward-looking statements” for the purpose of the safe harbor provided by Section 21E of the Securities Exchange Act of 1934, as amended (“Exchange Act”), and Section 27A of the Securities Act of 1933, as amended (“Securities Act”). In addition, words such as “estimate,” “anticipate,” “project,” “plan,” “intend,” “believe,” “expect,” “likely,” “predicted,” “positioned” and any variations of these words and similar expressions are intended to identify forward-looking statements. Such statements include plans, projections and estimates and are found at various places throughout this prospectus and the documents incorporated by reference herein. These forward-looking statements, including those relating to future business prospects, revenues and income, wherever they occur in this prospectus or documents incorporated by reference in this prospectus, are necessarily estimates reflecting the best judgment of our senior management and involve a number of risks and uncertainties that could cause actual results to differ materially from those suggested by the forward-looking statements. Such forward-looking statements should, therefore, be considered in light of various risks, uncertainties and assumptions, including prevailing market conditions and other important factors, including those set forth in or incorporated by reference in this prospectus. Important factors that could cause actual results to differ materially from estimates or projections contained in the forward-looking statements include those factors described in the sections entitled “Risk Factors” on page 3 of this prospectus and page 9 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2017, as updated by annual, quarterly and other reports and documents we file with the SEC after the date of this prospectus and that are incorporated by reference herein.

Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those expected. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this prospectus or the date of the documents incorporated by reference herein. You also should understand that it is not possible to predict or identify all such factors and that the risk factors as listed in our filings with the SEC should not be considered a complete statement of all potential risks and uncertainties. We undertake no obligation to update any forward-looking statements as a result of future events or developments. As used herein, the term “including,” and any variation thereof, means “including without limitation.” Unless the context otherwise requires, the use of the word “or” herein is not exclusive.

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SELLING SECURITY HOLDERS

We may register securities covered by this prospectus for re-offers and resales by any selling security holders to be named in a prospectus supplement. Because we are a well-known seasoned issuer, as defined in Rule 405 of the Securities Act, we may add secondary sales of securities by any selling security holders by filing a prospectus supplement with the SEC. We may register these securities to permit selling security holders to resell their securities when they deem appropriate. A selling security holder may resell all, a portion or none of their securities at any time and from time to time. We may register those securities for sale through an underwriter or other plan of distribution as set forth in a prospectus supplement. See “Plan of Distribution.” Selling security holders may also sell, transfer or otherwise dispose of some or all of their securities in transactions exempt from the registration requirements of the Securities Act. We may pay all expenses incurred with respect to the registration of the securities owned by the selling security holders, other than underwriting fees, discounts or commissions, which will be borne by the selling security holders. We will provide you with a prospectus supplement naming the selling security holders, the amount of securities to be registered and sold and other terms of the securities being sold by a selling security holder.

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USE OF PROCEEDS

Unless otherwise indicated in a prospectus supplement, we intend to use the net proceeds from the sale of our securities for general corporate purposes, repayment of indebtedness, the financing of possible acquisitions and investments or for such other purposes as may be specified in the applicable prospectus supplement. Unless otherwise set forth in a prospectus supplement, we will not receive any proceeds from any sales of our securities by any selling security holder to be named in a prospectus supplement.

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RATIO OF EARNINGS TO FIXED CHARGES AND EARNINGS TO COMBINED FIXED CHARGES AND DIVIDENDS ON PREFERRED STOCK AND LOSSES ON PURCHASES

OF PREFERRED STOCK

The following table sets forth our ratio of earnings to fixed charges, the excess of our earnings to cover fixed charges, our ratio of earnings to combined fixed charges and dividends on preferred stock and losses on purchases of preferred stock and the excess of our earnings to cover fixed charges and dividends on preferred stock and losses on purchases of preferred stock for the periods indicated.

	Year Ended December 31,
	2013		2014		2015		2016		2017
	(dollars in thousands)
Ratio of Earnings to Fixed Charges		1.3		1.4		1.6		1.5		1.5
Excess of Earnings to Cover Fixed Charges	$	249,169	$	332,085	$	469,024	$	366,844	$	459,048
Ratio of Earnings to Combined Fixed Charges and Dividends on Preferred Stock and Losses on Purchases of Preferred Stock		1.3		1.3		1.5		1.4		1.4
Excess of Earnings to Cover Fixed Charges and Dividends on Preferred Stock and Losses on Purchases of Preferred Stock	$	237,806	$	288,097	$	425,036	$	333,853	$	400,754

For purposes of computing the ratios of earnings to fixed charges and earnings to combined fixed charges and dividends on preferred stock and losses on purchases of preferred stock, earnings represent income before income taxes and fixed charges less interest capitalized. Fixed charges consist of interest expense, amortized premiums, discounts and capitalized expenses related to indebtedness, interest capitalized and the interest component of operating lease expense.

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DESCRIPTION OF DEBT SECURITIES

The following description of the terms of the debt securities sets forth certain general terms and provisions of the debt securities to which any prospectus supplement may relate. The particular terms of the debt securities offered by any prospectus supplement and the extent, if any, to which these general provisions may apply to those debt securities will be described in the prospectus supplement relating to those debt securities. Accordingly, for a description of the terms of a particular issue of debt securities, reference must be made to both the prospectus supplement relating thereto and to the following description. As used in this section, “CCIC,” “we,” “our” and “us” refer only to Crown Castle International Corp. and not to its consolidated subsidiaries. Capitalized terms used but not defined herein shall have the meanings assigned thereto in the indenture (as defined below).

We may issue debt securities from time to time in one or more series. The debt securities will represent direct, general obligations of CCIC. In the event that any series of debt securities will be subordinated to other indebtedness that we have outstanding or may incur, the terms of the subordination will be set forth in the prospectus supplement relating to the subordinated debt securities. Debt securities will be issued under one or more base indentures, together with related supplemental indentures or officers’ certificates, between us and The Bank of New York Mellon Trust Company, N.A., as trustee (collectively, as applicable, “indenture”), or another trustee named in the prospectus supplement. In addition to debt securities issued under the indenture described below, we may issue debt securities under the indenture dated as of April 15, 2014 between CCIC and The Bank of New York Mellon Trust Company, N.A., as trustee (“existing indenture”). The terms of the existing indenture and any debt securities issued thereunder will be set forth in the prospectus supplement relating to such debt securities. A copy of the form of the base indenture has been filed as an exhibit to the registration statement of which this prospectus forms a part and is incorporated by reference herein. The following discussion of certain provisions of the indenture is a summary only and should not be considered a complete description of the terms and provisions of the indenture. Accordingly, the following discussion is qualified in its entirety by reference to the provisions of the indenture.

General

The debt securities represent direct, general obligations of CCIC and:

• may rank equally with other unsubordinated debt or may be subordinated to other debt we have or may incur;

• may be issued in one or more series with the same or various maturities;

• may be issued at a price of 100% of their principal amount or at a premium or discount;

• may be issued in certificated or uncertificated form; and

• may be represented by one or more global securities registered in the name of a designated depositary’s nominee, and if so, beneficial interests in the global securities will be shown on and transfers will be made only through records maintained by the designated depositary and its participants.

The aggregate principal amount of debt securities that we may authenticate and deliver is unlimited. The debt securities may be issued in one or more series as we may authorize from time to time. You should refer to the applicable prospectus supplement for the following terms of the debt securities of the series with respect to which that prospectus supplement is being delivered:

• the title of the debt securities of the series (which shall distinguish the debt securities of that particular series from the debt securities of any other series);

• any limit upon the aggregate principal amount of the debt securities of the series that may be authenticated and delivered under the indenture (except for debt securities authenticated and delivered upon registration or transfer of, or in exchange for, or in lieu of, other debt securities of the series);

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• the date or dates on which the principal and premium with respect to the debt securities of the series are payable;

• the rate or rates (which may be fixed or variable) at which the debt securities of the series shall bear interest, if any, or the method of determining such rate or rates, the date or dates from which such interest, if any, shall accrue, the interest payment dates on which such interest, if any, shall be payable or the method by which such dates will be determined, any record dates and the basis upon which such interest will be calculated if other than that of a 360-day year of twelve 30-day months;

• the form of the debt securities of the series;

• the currency or currencies in which debt securities of the series shall be denominated, if other than U.S. dollars, the place or places, if any, in addition to or instead of the corporate trust office of the trustee, where the principal, premium and interest with respect to debt securities of such series shall be payable or the method of such payment, if by wire transfer, mail or other means;

• the price or prices at which, the period or periods within which, and the terms and conditions upon which, debt securities of the series may be redeemed, in whole or in part at our option or otherwise;

• if other than as provided in the indenture, our obligation, if any, to redeem, purchase or repay debt securities of the series pursuant to any sinking fund or analogous provisions or at the option of a holder of such debt securities and the price or prices at which, the period or periods within which, and the terms and conditions upon which, debt securities of the series shall be redeemed, purchased or repaid, in whole or in part, pursuant to such obligations;

• the terms, if any, upon which the debt securities of the series may be convertible into or exchanged for our common stock, preferred stock, other debt securities or warrants for common stock, preferred stock, indebtedness or other securities of any kind and the terms and conditions upon which such conversion or exchange shall be effected, including the initial conversion or exchange price or rate, the conversion or exchange period and any other additional provisions;

• if other than denominations of $2,000 or integral multiples of $1,000 in excess thereof, the denominations in which the debt securities of the series shall be issuable;

• if the amount of principal, premium or interest with respect to the debt securities of the series may be determined with reference to an index or pursuant to a formula, the manner in which such amounts will be determined;

• any changes or additions to the provisions of the indenture dealing with defeasance;

• if other than the principal amount thereof, the portion of the principal amount of debt securities of the series that shall be payable upon declaration of acceleration of the maturity thereof pursuant to the terms of the indenture or provable in bankruptcy;

• the terms, if any, of the transfer, mortgage, pledge or assignment as security for the debt securities of the series of any properties, assets, moneys, proceeds, securities or other collateral, including whether certain provisions of the Trust Indenture Act of 1939, as amended (“TIA”), are applicable and any corresponding changes to provisions of the indenture as then in effect;

• any addition to or change in the events of default with respect to the debt securities of the series and any change in the right of the trustee or the holders of such series of debt securities to declare the principal, premium and interest, if any, on such series of debt securities due and payable pursuant to the terms of the indenture;

• if other than as provided in the indenture, whether the debt securities of the series shall be issued in whole or in part in the form of a global security, the terms and conditions, if any, upon which such global security may be exchanged in whole or in part for other individual debt securities of such series in certificated form, the depositary (as defined in the applicable prospectus supplement) for such global security and the form of any legend or legends to be borne by any such global security in addition to or in lieu of the legend referred to in the indenture;

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• if the trustee, paying agent or registrar of a series is other than the trustee initially named in the indenture;

• the applicability of, and any addition to or change in, the covenants and definitions set forth in the indenture or in the terms then set forth in the indenture relating to permitted consolidations, mergers or sales of assets which apply to debt securities of the series;

• the terms, if any, of any guarantee of the payment of principal, premium and interest with respect to debt securities of the series and any corresponding changes to the provisions of the indenture as then in effect;

• whether the debt securities of a series will be secured by any collateral and, if so, the terms and conditions upon which such debt securities shall be secured and, if applicable, upon which such liens may be subordinated to other liens securing other indebtedness of CCIC or any guarantor;

• the subordination, if any, of the debt securities of the series pursuant to the indenture and any changes or additions to the provisions of the indenture then in effect;

• with regard to debt securities of a series that do not bear interest, the dates for certain required reports to the trustee; and

• any other terms of the debt securities of the series subject, if applicable, to the applicable provisions of the indenture.

The prospectus supplement will also describe any material U.S. federal income tax consequences or other special considerations applicable to the series of debt securities to which such prospectus supplement relates, including those applicable to:

• debt securities with respect to which payments of principal, premium or interest are determined with reference to an index or formula (including changes in prices of particular securities, currencies or commodities);

• debt securities with respect to which principal or interest is payable in a foreign or composite currency;

• debt securities that are issued at a discount below their stated principal amount, bearing no interest or interest at a rate that at the time of issuance is below market rates; and

• variable rate debt securities that are exchangeable for fixed rate debt securities.

All funds that we pay to a paying agent for the payment of principal, premium or interest with respect to any debt securities that remain unclaimed at the end of two years after that principal, premium or interest shall have become due and payable will be repaid to us, and the holders of those debt securities or any related coupons will thereafter look only to us for payment thereof.

Paying Agent and Registrar for the Notes

Unless otherwise provided in the applicable prospectus supplement with respect to a series of debt securities, (1) the trustee will initially act as the paying agent and registrar for each series of debt securities, (2) CCIC may change the paying agent or registrar under the indenture without prior notice to the holders and (3) CCIC or any of its subsidiaries may act as paying agent or registrar under the indenture.

Transfer and Exchange

Unless otherwise provided in the applicable prospectus supplement with respect to a series of debt securities, the following provisions will apply for each series of debt securities.

A holder may transfer or exchange debt securities in accordance with the indenture. The registrar and the trustee may require a holder to furnish appropriate endorsements and transfer documents in connection with a

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transfer of debt securities. Holders will be required to pay all taxes due on transfer. CCIC is not required to transfer or exchange any debt securities selected for redemption. Also, CCIC is not required to transfer or exchange any debt securities for a period of 15 days before a selection of debt securities to be redeemed.

Book-Entry, Delivery and Form

Unless otherwise provided in the applicable prospectus supplement with respect to a series of debt securities, the following provisions will apply for each series of debt securities.

The debt securities will be initially issued in the form of one or more global securities (collectively, the “global securities”) registered in the name of The Depository Trust Company (“DTC”) or its nominee.

Upon the issuance of a global security, DTC or its nominee will credit the accounts of Persons holding through it with the respective principal amounts of the debt securities represented by such global security purchased by such Persons. Such accounts shall be designated by the underwriters. Ownership of beneficial interests in a global security will be limited to Persons that have accounts with DTC (“participants”) or Persons that may hold interests through participants. Ownership of beneficial interests in a global security will be shown on, and the transfer of that ownership interest will be effected only through, records maintained by DTC or its nominee (with respect to participants’ interests) and such participants (with respect to the owners of beneficial interests in such global security other than participants). The laws of some jurisdictions require that certain purchasers of securities take physical delivery of such securities in certificated form. Such limits and such laws may impair the ability to transfer beneficial interests in a global security.

Notwithstanding anything to the contrary contained in this “Description of Debt Securities,” as long as the debt securities are in the form of a global security, notice to the holders may be made electronically in accordance with procedures of DTC or any successor thereto.

Payment of principal of and interest on debt securities represented by a global security will be made in immediately available funds to DTC or its nominee, as the case may be, as the sole registered owner and the sole holder of the debt securities represented thereby for all purposes under the indenture. CCIC has been advised by DTC that upon receipt of any payment of principal of or interest on any global security, DTC or its nominee will immediately credit, on its book-entry registration and transfer system, the accounts of participants with payments in amounts proportionate to their respective beneficial interests in the principal or face amount of such global security as shown on the records of DTC or its nominee. Payments by participants to owners of beneficial interests in a global security held through such participants will be governed by standing instructions and customary practices as is now the case with securities held for customer accounts registered in “street name” and will be the sole responsibility of such participants.

A global security may not be transferred except as a whole by DTC or a nominee of DTC to DTC or to a nominee of DTC. A global security is exchangeable for certificated debt securities only if:

• DTC notifies CCIC that it is unwilling or unable to continue as a depositary for such global security or if at any time DTC ceases to be a clearing agency registered under the Exchange Act;

• CCIC, in its discretion, at any time determines not to have all the debt securities represented by such global security; or

• there shall have occurred and be continuing a default or an Event of Default with respect to the debt securities represented by such global security.

Any global security that is exchangeable for certificated debt securities pursuant to the preceding sentence will be exchanged for certificated debt securities in authorized denominations and registered in such names as DTC or any successor depositary holding such global security may direct. Subject to the foregoing, a global

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security is not exchangeable, except for a global security of like denomination to be registered in the name of DTC or any successor depositary or its nominee. In the event that a global security becomes exchangeable for certificated debt securities,

• certificated debt securities will be issued only in fully registered form in denominations of $2,000 and integral multiples of $1,000 in excess thereof;

• payment of principal of, and premium, if any, and interest on, the certificated debt securities will be payable, and the transfer of the certificated debt securities will be registrable, at the office or agency of CCIC maintained for such purposes; and

• no service charge will be made for any registration of transfer or exchange of the certificated debt securities, although CCIC may require payment of a sum sufficient to cover any tax or governmental charge imposed in connection therewith.

So long as DTC or any successor depositary for a global security, or any nominee, is the registered owner of such global security, DTC or such successor depositary or nominee, as the case may be, will be considered the sole holder of the debt securities represented by such global security for all purposes under the indenture and the debt securities of the applicable series. Except as set forth above, owners of beneficial interests in a global security will not be entitled to have the debt securities represented by such global security registered in their names, will not receive or be entitled to receive physical delivery of debt securities in certificated form and will not be considered to be the holders of any debt securities under such global security. Accordingly, each Person owning a beneficial interest in a global security must rely on the procedures of DTC or any successor depositary, and, if such Person is not a participant, on the procedures of the participant through which such Person owns its interest, to exercise any rights of a holder under the indenture. CCIC understands that under existing industry practices, in the event that CCIC requests any action of holders or that an owner of a beneficial interest in a global security desires to give or take any action which a holder is entitled to give or take under the indenture, DTC or any successor depositary would authorize the participants holding the relevant beneficial interest to give or take such action and such participants would authorize beneficial owners owning through such participants to give or take such action or would otherwise act upon the instructions of beneficial owners owning through them.

DTC has advised CCIC that DTC is a limited-purpose trust company organized under the Banking Law of the State of New York, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered under the Exchange Act. DTC was created to hold the securities of its participants and to facilitate the clearance and settlement of securities transactions among its participants in such securities through electronic book-entry changes in accounts of the participants, thereby eliminating the need for physical movement of securities certificates. DTC’s participants include securities brokers and dealers (which may include the underwriters), banks, trust companies, clearing corporations and certain other organizations, some of whom (or their representatives) own DTC. Access to DTC’s book-entry registration and transfer system is also available to others, such as banks, brokers, dealers and trust companies that clear through or maintain a custodial relationship with a participant, either directly or indirectly.

Although DTC has agreed to the foregoing procedures in order to facilitate transfers of interests in global securities among participants of DTC, it is under no obligation to perform or continue to perform such procedures, and such procedures may be discontinued at any time. None of CCIC, the trustee or the underwriters will have any responsibility for the performance by DTC or its participants or indirect participants of their respective obligations under the rules and procedures governing their operations.

Selection and Notice

Unless otherwise provided in the applicable prospectus supplement with respect to a series of debt securities, the following provisions will apply to any redemption of debt securities under the indenture.

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If less than all of the debt securities of a series are to be redeemed at any time, the debt securities to be redeemed will be selected in accordance with the procedures of the depositary, which initially is DTC or its successor or nominee.

No debt securities of $2,000 of principal amount or less will be redeemed in part. Notices of redemption will be sent by electronic transmission or first class mail at least 30 but not more than 60 days before the redemption date to each holder of debt securities to be redeemed at its registered address or otherwise in accordance with the applicable procedures of the depositary. Notices of redemption may be conditional and, at our discretion, the redemption date may be delayed until such time as any or all such conditions shall be satisfied.

If any debt security is to be redeemed in part only, the notice of redemption that relates to such debt security shall state the portion of the principal amount of that debt security to be redeemed. A new debt security in principal amount equal to the unredeemed portion of the original debt security presented for redemption will be issued in the name of the holder thereof upon cancellation of the original debt security. Debt securities called for redemption, subject to any condition included in such notice of redemption, become due on the date fixed for redemption. On and after the redemption date, interest ceases to accrue on such debt securities or portions of them called for redemption unless CCIC defaults on payment of the redemption price.

Subordination

Debt securities of a series may be subordinated, which we refer to as subordinated debt securities, to senior indebtedness (as defined in the applicable prospectus supplement) to the extent set forth in the prospectus supplement relating thereto. To the extent we conduct operations through subsidiaries, the holders of debt securities (whether or not subordinated debt securities) will be structurally subordinated to the creditors of our subsidiaries.

Certain Covenants

Below is a summary of certain covenants for the benefit of holders of each series of debt securities under the indenture unless otherwise provided in the applicable prospectus supplement. If debt securities are issued, the indenture, as supplemented for a particular series of debt securities, may contain certain additional covenants for the benefit of the holders of such series of debt securities, which will be applicable (unless waived or amended) so long as any of the debt securities of such series are outstanding, unless stated otherwise in the applicable prospectus supplement. The specific terms of these additional covenants, and summaries thereof, will be set forth in the prospectus supplement relating to such series of debt securities.

Merger, Consolidation and Sale of Assets

The indenture provides that we may not:

(1)    consolidate or merge with or into (whether or not CCIC is the surviving corporation); or

(2)    sell, assign, transfer, lease, convey or otherwise dispose of all or substantially all of our properties or assets in one or more related transactions to, another corporation, Person or entity, unless:

(a)    either:

(i)    CCIC is the surviving corporation; or

(ii)    the entity or the Person formed by or surviving any such consolidation or merger (if other than CCIC) or to which the sale, assignment, transfer, lease, conveyance or other disposition shall have been made is a Person (which, if not a corporation, includes a corporate co-issuer) organized or existing under the laws of the United States, any state thereof or the District of Columbia;

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(b)    the entity or Person formed by or surviving any such consolidation or merger (if other than CCIC) or the entity or Person to which the sale, assignment, transfer, lease, conveyance or other disposition shall have been made assumes all the obligations of CCIC under the debt securities and the indenture pursuant to a supplemental indenture in a form reasonably satisfactory to the trustee; and

(c)    immediately after such transaction no default or Event of Default shall have occurred and be continuing.

SEC Reports

Whether or not required by the SEC’s rules and regulations, so long as any debt securities are outstanding, CCIC will furnish to the trustee, within 15 days after CCIC is required to file (or would be required to file assuming it were subject to such requirements and including any extensions thereof) such annual and quarterly reports, information, documents and other reports with the SEC, copies of CCIC’s annual report and of the information, documents and other reports that CCIC is required to file (or would be required to file assuming it were subject to such requirements and including any extensions thereof) with the SEC pursuant to Section 13 or 15(d) of the Exchange Act. CCIC will also comply with the applicable provisions of Section 314(a) of the TIA. To the extent such filings are made with the SEC, the reports will be deemed to be furnished to the trustee and holders.

In the event that the rules and regulations of the SEC permit CCIC and any direct or indirect parent of CCIC to report at such parent entity’s level on a consolidated basis and such parent entity is not engaged in any business in any material respect other than incidental to its ownership, directly or indirectly, of the capital stock of CCIC, consolidating reporting at the parent entity’s level in a manner consistent with that described in this covenant for CCIC will satisfy this covenant, and the indenture will permit CCIC to satisfy its obligations in this covenant with respect to financial information relating to CCIC by furnishing financial information relating to such direct or indirect parent; provided that such financial information is accompanied by consolidating information that explains in reasonable detail the differences between the information relating to such direct or indirect parent and any of its Subsidiaries other than CCIC and its Subsidiaries, on the one hand, and the information relating to CCIC and its Subsidiaries on a standalone basis, on the other hand.

Events of Default and Remedies

Each of the following constitutes an “Event of Default” under the indenture with respect to any series of debt securities:

(1) default for 30 days in the payment when due of interest on the debt securities of the applicable series;

(2) default in payment when due of the principal of or premium, if any, on the debt securities of the applicable series;

(3) failure by CCIC or any of its Subsidiaries to comply with the provisions described under the caption “Certain Covenants—Merger, Consolidation and Sale of Assets”;

(4) failure by CCIC or any of its Subsidiaries for 60 days (or 120 days in the case of a failure to comply with the reporting obligations described under the caption “Certain Covenants—SEC Reports”) after notice to comply with any of its other applicable agreements in the indenture or the debt securities of the applicable series;

(5) default under any indebtedness for money borrowed by CCIC or any of its Significant Subsidiaries, or the payment of which is guaranteed by CCIC or any of its Significant Subsidiaries, whether such indebtedness or guarantee now exists, or is created after the date of the indenture, which default:

(a) is caused by a failure to pay principal of or premium, if any, or interest on the indebtedness prior to the expiration of the grace period provided in such indebtedness on the date of the default (a “Payment Default”); or

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(b) results in the acceleration of the indebtedness prior to its express maturity, and, in each case, the principal amount of any such indebtedness, together with the principal amount of any other such indebtedness under which there has been a Payment Default or the maturity of which has been so accelerated, aggregates $250 million or more;

(6) failure by CCIC or any of its Significant Subsidiaries to pay final judgments aggregating (net of amounts covered by insurance policies) in excess of $250 million, which judgments are not paid, discharged or stayed for a period of 60 days; or

(7) certain events of bankruptcy or insolvency described in the indenture with respect to CCIC or any of its Subsidiaries.

A prospectus supplement may omit, modify or add to the foregoing Events of Default with respect to the applicable series of debt securities.

However, a default under clause (4) above will not constitute an Event of Default for any series of debt securities until the trustee or the holders of 25% in principal amount of the outstanding debt securities of such series notify CCIC of the default and CCIC does not cure such default within the time specified after receipt of such notice.

If any Event of Default occurs and is continuing, the trustee or the holders of at least 25% in principal amount of the then outstanding debt securities of the applicable series may declare all such debt securities to be due and payable immediately. Notwithstanding the foregoing, in the case of an Event of Default arising from certain events of bankruptcy or insolvency, with respect to CCIC, all outstanding debt securities will become due and payable without further action or notice. Holders of the debt securities may not enforce the indenture or the debt securities except as provided in the indenture. Subject to certain limitations, holders of a majority in principal amount of the then-outstanding debt securities of any series may direct the trustee in its exercise of any trust or power.

The holders of a majority in aggregate principal amount of the debt securities then outstanding of any series by notice to the trustee may, on behalf of the holders of all the debt securities of such series, waive any existing default or Event of Default and its consequences under the indenture with respect to such series, except a continuing default or Event of Default in the payment of interest on, or the principal of, the debt securities of such series.

Subject to the provisions of the indenture relating to the duties of the trustee in case an event of default shall occur and be continuing, the trustee is under no obligation to exercise any of its rights or powers under the indenture or debt securities at the request or direction of any of the holders of any series of debt securities, unless such holders have offered to the trustee indemnity or security satisfactory to it against any loss, liability or expense. Subject to such provisions for the indemnification of the trustee, the holders of at least a majority in aggregate principal amount of the outstanding debt securities of a series have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to such series of debt securities. The trustee, however, may refuse to follow any direction that conflicts with law or the indenture or that the trustee determines is unduly prejudicial to the rights of any other holder of such series of debt securities or that would involve the trustee in personal liability. Prior to taking any action under the indenture, the trustee is entitled to indemnification satisfactory to it in its sole discretion against all losses and expenses caused by taking or not taking such action.

The indenture provides that if a default or Event of Default occurs and is continuing with respect to a series of debt securities and is known to the trustee, the trustee must send to each holder of the debt securities of such series a notice of the default within 90 days after it occurs. Except in the case of a default or an Event of Default in the payment of principal of or interest on any debt security, the trustee may withhold notice if and so long as a committee of its trust officers determines in good faith that withholding notice is in the interest of the holders of

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such debt securities. In addition, CCIC is required to deliver to the trustee, within 90 days after the end of each fiscal year, a statement by certain of our officers as to whether or not we, to their knowledge, are in default in the performance or observance of any of the terms, provisions and conditions of the indenture and, if so, specifying all such known defaults. CCIC is also required to deliver to the trustee, promptly after the occurrence thereof, written notice of any event that would constitute a default or Event of Default, the status thereof and what action CCIC is taking or proposes to take in respect thereof.

Street name and other indirect holders should consult their banks and brokers for information on their requirements for giving notice or taking other actions upon a default.

No Personal Liability of Directors, Officers, Employees and Stockholders

No director, officer, employee, incorporator or stockholder of CCIC, as such, shall have any liability for any obligations of CCIC under the debt securities, the indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each holder by accepting a debt security waives and releases all such liability. The waiver and release are part of the consideration for issuance of the debt securities. The waiver may not be effective to waive liabilities under the federal securities laws and it is the view of the SEC that such a waiver is against public policy.

Legal Defeasance and Covenant Defeasance

CCIC may, at its option and at any time, elect to have all of its obligations discharged with respect to the debt securities of any series outstanding (“Legal Defeasance”), except for the following provisions, which shall survive until otherwise terminated or discharged under the indenture:

(1) the rights of holders of outstanding debt securities of the applicable series to receive payments in respect of the principal of, premium, if any, and interest on the debt securities of such series when such payments are due from the trust referred to below;

(2) CCIC’s obligations with respect to the debt securities of such series concerning issuing temporary debt securities, registration of debt securities, mutilated, destroyed, lost or stolen debt securities and the maintenance of an office or agency for payment and money for security payments held in trust;

(3) the rights, powers, trusts, duties and immunities of the trustee, and CCIC’s obligations in connection therewith; and

(4) the Legal Defeasance provisions of the indenture.

In addition, CCIC may, at its option and at any time, elect to have the obligations of CCIC released with respect to certain covenants that are described in the indenture and any additional covenants contained in the applicable supplemental indenture (“Covenant Defeasance”) with respect to the debt securities of any series and thereafter any omission to comply with such obligations shall not constitute a default or Event of Default with respect to the debt securities of such series. In the event Covenant Defeasance occurs with respect to the debt securities of any series, certain events described under “Events of Default and Remedies,” but not including nonpayment and bankruptcy, receivership, rehabilitation and insolvency events with respect to CCIC, will no longer constitute an Event of Default with respect to the debt securities of such series.

In order to exercise either Legal Defeasance or Covenant Defeasance:

(1) CCIC must irrevocably deposit with the trustee, in trust, for the benefit of the holders of the debt securities of the applicable series, cash in United States dollars, non-callable Government Securities, or a combination thereof, in such amounts as will be sufficient, in the opinion of a nationally recognized firm of independent public accountants, to pay the principal of, premium, if any, and interest on the outstanding debt securities of such series on the stated date for payment thereof or on the applicable redemption date, as the case may be, and CCIC must specify whether the debt securities of such series are being defeased to maturity or to a particular redemption date;

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(2) in the case of Legal Defeasance, CCIC shall have delivered to the trustee an opinion of counsel in the United States reasonably acceptable to the trustee confirming that:

(a) CCIC has received from, or there has been published by, the Internal Revenue Service a ruling; or

(b) since the initial issue date of such series of securities, there has been a change in the applicable federal income tax law,

in either case to the effect that, and based thereon such opinion of counsel shall confirm that, the holders of the outstanding debt securities of the applicable series will not recognize income, gain or loss for federal income tax purposes as a result of such Legal Defeasance and will be subject to federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such Legal Defeasance had not occurred;

(3) in the case of Covenant Defeasance, CCIC shall have delivered to the trustee an opinion of counsel of a nationally recognized law firm in the United States confirming that the holders of the outstanding debt securities of the applicable series will not recognize income, gain or loss for federal income tax purposes as a result of such Covenant Defeasance and will be subject to federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such Covenant Defeasance had not occurred;

(4) no default or Event of Default shall have occurred and be continuing with respect to the outstanding debt securities of the applicable series either:

(a) on the date of such deposit, other than a default or Event of Default resulting from the borrowing of funds to be applied to such deposit; or

(b) insofar as Events of Default from bankruptcy or insolvency events with respect to CCIC are concerned, at any time in the period ending on the 91st day after the date of deposit;

(5) such Legal Defeasance or Covenant Defeasance will not result in a breach or violation of, or constitute a default under any material agreement or instrument, other than the indenture with respect to the outstanding debt securities of the applicable series, to which CCIC or any of its Subsidiaries is a party or by which CCIC or any of its Subsidiaries is bound;

(6) CCIC must have delivered to the trustee an opinion of counsel to the effect that after the 91st day following the deposit, the trust funds will not be subject to the effect of any applicable bankruptcy, insolvency, reorganization or similar laws affecting creditors’ rights generally;

(7) CCIC must deliver to the trustee an officers’ certificate stating that the deposit was not made by CCIC with the intent of preferring the holders of the debt securities of the applicable series over any other creditors of CCIC or with the intent of defeating, hindering, delaying or defrauding creditors of CCIC or others; and

(8) CCIC must deliver to the trustee an officers’ certificate and an opinion of counsel, each stating that all conditions precedent provided for or relating to the Legal Defeasance or the Covenant Defeasance with respect to the debt securities of the applicable series have been complied with.

Satisfaction and Discharge

The indenture will cease to be of further effect (except as to surviving rights of transfer or exchange of the applicable debt securities, as expressly provided for in the indenture) with respect to the debt securities of any series when (a) CCIC delivers to the trustee for cancellation all debt securities of such series or (b) all outstanding debt securities of such series not delivered to the trustee for cancellation become due and payable, or are by their terms to become due and payable within one year or are to be called for redemption within one year, and CCIC deposits with the trustee as trust funds the entire amount sufficient to pay at maturity or upon redemption of all outstanding debt securities of such series.

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Amendment, Supplement and Waiver

Except as described in the two paragraphs below, the holders of a majority in principal amount of the debt securities outstanding of any series can, with respect to the debt securities of such series:

(1) consent to any amendment or supplement to the indenture or the debt securities of such series; and

(2) waive any existing default or Event of Default under, or the compliance with any provisions of, the indenture or the debt securities of such series.

Consents and waivers obtained in connection with a purchase of, or tender offer or exchange offer for, such debt securities shall be included for purposes of the previous sentence.

Without the consent of each holder of each outstanding debt security of any series affected, an amendment or waiver with respect to any debt securities of the applicable series held by a non-consenting holder may not:

(1) reduce the principal amount of such debt securities whose holders must consent to an amendment, supplement or waiver;

(2) reduce the principal of or change the fixed maturity of any such debt security or alter the provisions with respect to the redemption (other than the notice period) of such debt securities;

(3) reduce the rate of or extend the time for payment of interest on any such debt securities;

(4) waive a default or Event of Default in the payment of principal of or premium, if any, or interest on such debt securities, excluding a rescission of acceleration of the debt securities of such series by the holders of at least a majority in aggregate principal amount of the debt securities of such series and a waiver of the Payment Default that resulted from such acceleration;

(5) make any such debt security payable in money other than that stated in the debt securities of the applicable series;

(6) make any change in the provisions of the indenture relating to waivers of past defaults or Events of Default or the rights of holders to receive payments of principal of or premium, if any, or interest on the debt securities of the applicable series;

(7) waive a redemption payment with respect to such debt securities; or

(8) make any change in the foregoing amendment and waiver provisions.

Notwithstanding the foregoing, without the consent of any holder, CCIC and the trustee may amend or supplement the indenture with respect to the debt securities of the applicable series to:

(1) cure any ambiguity, omission, defect or inconsistency;

(2) provide for uncertificated debt securities in addition to or in place of certificated debt securities;

(3) provide for the assumption of CCIC’s obligations to holders of debt securities of the applicable series in the case of a merger or consolidation;

(4) make any change that would provide any additional rights or benefits to the holders of such series of debt securities or that does not adversely affect the legal rights under the indenture of any such holder of such series of debt securities in any material respect;

(5) comply with requirements of the SEC in order to effect or maintain the qualification of the indenture or any supplemental indenture under the TIA;

(6) conform a provision of the indenture or supplemental indenture to the extent such provision was intended to be a substantially verbatim recitation of the applicable provision in this “Description of Debt Securities” or under the caption “Description of Notes” (or comparable section) in any prospectus supplement, as applicable;

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(7) in the case of subordinated debt securities, to make any change in the provisions of the indenture or any supplemental indenture relating to subordination that would limit or terminate the benefits available to any holder of senior indebtedness under such provisions (but only if each such holder of senior indebtedness consents to such change);

(8) add guarantees with respect to the debt securities or to secure the debt securities;

(9) add to, change, or eliminate any of the provisions of the indenture with respect to one or more series of debt securities, so long as any such addition, change or elimination not otherwise permitted under the indenture shall (A) neither apply to any debt security of any series created prior to the execution of such supplemental indenture and entitled to the benefit of such provision nor modify the rights of the holders of any such debt security with respect to the benefit of such provision or (B) become effective only when there is no such debt security outstanding;

(10) evidence and provide for the acceptance of appointment by a successor or separate trustee with respect to the debt securities of one or more series and to add to or change any of the provisions of the indenture as shall be necessary to provide for or facilitate the administration of the indenture by more than one trustee; or

(11) establish the form or terms of debt securities and coupons of any series, as described under “General” above.

Concerning the Trustee

The indenture provides that, except during the continuance of an event of default, the trustee will perform only such duties as are specifically set forth in the indenture. During the existence of an event of default, the trustee will exercise such rights and powers vested in it under the indenture and use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person’s own affairs. The indenture and provisions of the Trust Indenture Act that are incorporated by reference therein contain limitations on the rights of the trustee, should it become a creditor of CCIC, to obtain payment of claims in certain cases, or to realize on certain property received in respect of any such claim as security or otherwise. The trustee will be permitted to engage in other transactions; however, if it acquires any conflicting interest, it must eliminate such conflict within 90 days, apply to the SEC for permission to continue or resign.

The holders of a majority in principal amount of the debt securities then outstanding of any series will have the right to direct the time, method and place of conducting any proceeding for exercising any remedy available to the trustee under the indenture with respect to the debt securities of such series, subject to certain exceptions. The indenture provides that if an Event of Default occurs and is not cured, the trustee will be required, in the exercise of its power, to use the degree of care of a prudent person in the conduct of such person’s own affairs. Subject to these provisions, the trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request of any holder of debt securities, unless that holder shall have offered to the trustee security and indemnity satisfactory to it against any loss, liability or expense.

Governing Law

The indenture and the debt securities will be governed by the laws of the State of New York.

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DESCRIPTION OF CAPITAL STOCK

The following descriptions set forth certain general terms of our common stock, our 6.875% Mandatory Convertible Preferred Stock, Series A, par value $0.01 per share (“Mandatory Convertible Preferred Stock”), and our authorized but unissued preferred stock. While we believe that the following description covers the material terms of our capital stock, the descriptions may not contain all of the information that is important to you. The descriptions set forth below are not complete and are subject to, and qualified in their entirety by, our Restated Certificate of Incorporation (“Charter”), our amended and restated by-laws (“By-laws”), the General Corporation Law of the State of Delaware (“DGCL”), the Certificate of Designations of our Mandatory Convertible Preferred Stock (“Certificate of Designations”) and, for any other series of preferred stock, the certificate of designations relating to such particular series of preferred stock. The particular terms of any series of preferred stock offered by any prospectus supplement and the extent, if any, to which these general provisions may apply to that series of preferred stock will be described in the prospectus supplement relating to that series of preferred stock. Copies of our Charter and By-laws and the Certificate of Designations have been filed as exhibits to the registration statement of which this prospectus forms a part. You are urged to read the Charter, the By-laws and the Certificate of Designations in their entirety. As used in this Section, unless otherwise expressly stated or the context otherwise requires, the terms “Company,” “Crown Castle,” “we,” “our” and “us” refer to Crown Castle International Corp. and not to any of its subsidiaries.

Authorized Capital

Our authorized capital stock consists of 600,000,000 shares of common stock, par value $0.01 per share, and 20,000,000 shares of preferred stock, par value $0.01 per share. As of March 22, 2018, there were 414,818,909 shares of our common stock outstanding and 1,649,998 shares of our Mandatory Convertible Preferred Stock outstanding.

Our common stock is listed for trading on the NYSE under the trading symbol “CCI” and our Mandatory Convertible Preferred Stock is listed for trading on the NYSE under the trading symbol “CCI-PA.”

Common Stock

Voting Rights

Each share of our common stock is entitled to one vote. Holders of our common stock vote together as a single class on all matters presented for a vote of the stockholders, except as provided under the DGCL. See also “—Charter and By-laws—Election and Removal of Directors” below.

Dividends and Liquidation Rights

Each share of our common stock is entitled to receive dividends if, as and when declared by our board of directors out of funds legally available for that purpose, subject to certain rights of holders of preferred stock, including the rights of holders of Mandatory Convertible Preferred Stock. In the event of our voluntary or involuntary liquidation, dissolution or winding up, after satisfaction of amounts payable to our creditors and distribution of any preferential amounts to the holders of outstanding preferred stock, including Mandatory Convertible Preferred Stock, holders of our common stock are entitled to share ratably in the assets available for distribution to the stockholders.

Other Provisions

The holders of our common stock have no preemptive, subscription or redemption rights and are not entitled to the benefit of any sinking fund. All outstanding shares of common stock are validly issued, fully paid and nonassessable. Under the DGCL, stockholders generally are not personally liable for a corporation’s acts or debts.

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Preferred Stock

Under the Charter, our board of directors is authorized, without further stockholder action, to issue up to 20,000,000 shares of preferred stock, par value $0.01 per share, in one or more series by filing a certificate of designations with the Secretary of State of the State of Delaware. Such certificate of designations may set forth the designations, powers, preferences and rights of the shares of each such series of preferred stock and the qualifications, limitations and restrictions thereof, including the dividend rate, the redemption provisions, if any, the amount payable in the event of our voluntary or involuntary liquidation, winding-up or dissolution, the terms and conditions, if any, of conversion and the voting rights. We have filed the Certificate of Designations with the Secretary of State of the State of Delaware to create the Mandatory Convertible Preferred Stock described below.

Mandatory Convertible Preferred Stock

The Mandatory Convertible Preferred Stock is a series of our preferred stock and impacts the rights of holders of our common stock. Each share of Mandatory Convertible Preferred Stock, unless previously converted, will automatically convert on August 1, 2020 into a number of shares of our common stock based on a specified conversion rate, which is subject to adjustment from time to time. The expected quarterly dividend on the Mandatory Convertible Preferred Stock, when, as and if declared, is $17.1875 per share (based on the annual dividend rate of 6.875% and a liquidation preference of $1,000.00 per share). Declared dividends on the Mandatory Convertible Preferred Stock are payable quarterly on February 1, May 1, August 1 and November 1 of each year to and including August 1, 2020. A further description of the terms of our Mandatory Convertible Preferred Stock is set forth in the Capital Stock Description (as defined in “—Where You Can Find More Information”) and incorporated by reference herein and is subject to, and qualified in its entirety by, the full terms of the Certificate of Designations contained in Exhibit 4.2 to the registration statement of which this prospectus forms a part.

Charter and By-laws

Stockholders’ rights and related matters are governed by the DGCL, our Charter and our By-laws. Certain provisions of our Charter and By-laws, descriptions of which are summarized or otherwise incorporated within this prospectus, may have the effect, either alone or in combination with each other, of discouraging or making more difficult a tender offer or takeover attempt that is opposed by our board of directors but that a stockholder might consider to be in its best interest. Such provisions may also adversely affect prevailing market prices for our capital stock. We believe that such provisions are necessary to enable us to develop our business in a manner that will foster our long-term growth without disruption caused by the threat of a takeover not deemed by our board of directors to be in our best interests and those of our stockholders.

Election and Removal of Directors

The Charter provides for the annual election of directors on our board of directors.

The Charter also provides that any director, except for directors who may be elected by the holders of any series of preferred stock, may be removed from office at any time, with or without cause, only by the affirmative vote of the holders of at least 80% of the voting power of the then outstanding Voting Stock, voting together as a single class. “Voting Stock” is defined in the Charter as the outstanding shares of our capital stock entitled to vote in a general vote of our stockholders as a single class with shares of our common stock.

No Stockholder Action by Written Consent; Special Meeting

The Charter prohibits stockholders from taking action by written consent in lieu of an annual or special meeting, and, thus, stockholders may only take action at an annual or special meeting called in accordance with the By-laws. The By-laws provide that special meetings of stockholders may only be called by (a) our secretary, chief executive officer or president at the direction of our board of directors pursuant to a resolution adopted by the board or (b) the chief executive officer.

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These provisions could have the effect of delaying consideration of a stockholder proposal until the next annual meeting. These provisions would also prevent the holders of a majority of the voting power of our capital stock entitled to vote from unilaterally using the written consent procedure to take stockholder action.

Advance Notice Requirements for Stockholder Proposals and Director Nominations; Proxy Access

The By-laws establish advance notice procedures for stockholder proposals and the nomination, other than by or at the direction of the board of directors, of candidates for election as directors. These procedures provide that the notice of stockholder proposals and stockholder nominations for the election of directors at an annual meeting must be in writing and received by our secretary at least 90 days but not more than 120 days prior to the first anniversary of our preceding year’s annual meeting. However, if the date of our annual meeting is more than 30 days earlier than, or more than 90 days later than, the anniversary date of our preceding year’s annual meeting, notice by a stockholder will be considered timely if it is delivered not earlier than the 120th day prior to such annual meeting and not later than the later of the 90th day prior to such annual meeting or the 10th day following the day on which public disclosure of the date of the annual meeting was made. The notice of nominations for the election of directors must set forth certain information concerning the stockholder giving the notice and each nominee.

By requiring advance notice of nominations by stockholders, these procedures afford our board of directors an opportunity to consider the qualifications of the proposed nominees and, to the extent deemed necessary or desirable by the board of directors, to inform stockholders about these qualifications. By requiring advance notice of other proposed business, these procedures provide our board of directors with an opportunity to inform stockholders of any business proposed to be conducted at a meeting, together with any recommendations as to the board of directors’ position on action to be taken on such business. This should allow stockholders to better decide whether to attend a meeting or to grant a proxy for the disposition of any such business.

Our By-laws also contain a proxy access right provision to permit a stockholder, or group of up to 20 stockholders, who owns (and continues to own) 3% or more of our common stock and has continuously owned our common stock for at least three years to nominate and include in our proxy materials candidates for election as directors of the Company. Such stockholders or groups of stockholders may nominate up to the greater of two individuals or 20% of the board of directors, provided that the stockholders and the nominees satisfy the notice requirements specified in the By-laws and comply with the other procedural requirements.

Dilution

The Charter provides that our board of directors is authorized to create and issue, whether or not in connection with the issuance and sale of any of its stock or other securities or property, rights entitling the holders to purchase from us shares of stock or other securities of us or of any other corporation. Our board of directors is authorized to issue these rights even though the creation and issuance of these rights could have the effect of discouraging third parties from seeking, or impairing their right to seek, to:

• acquire a significant portion of our outstanding securities;

• engage in any transaction which might result in a change of control of the corporation; or

• enter into any agreement, arrangement or understanding with another party to accomplish these transactions or for the purpose of acquiring, holding, voting or disposing of any of our securities.

Amendments

The Charter and the By-laws provide that we may amend, alter, change or repeal any provision contained in the Charter or a preferred stock designation. However, the affirmative vote of the holders of at least 80% of the voting power of the then outstanding voting stock, voting together as a single class, is required to amend, repeal

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or adopt any provision inconsistent with certain provisions of the Charter, including the provisions discussed above relating to the issuance of stockholder rights, prohibiting stockholder action by written consent and prohibiting the calling of special meetings by stockholders.

The By-laws may be amended by either the holders of 80% of the voting power of the voting stock or by the majority of the board, but the board may alter, amend or repeal or adopt new by-laws in conflict with certain of the By-law provisions only by a two-thirds vote of the entire board.

Section 203 of the Delaware General Corporation Law

We are subject to the provisions of Section 203 of the DGCL which generally prohibit certain transactions between a Delaware corporation and an interested stockholder for a period of three years after the date such interested stockholder acquired its stock, unless:

• the business combination is approved by the corporation’s board of directors prior to the date the interested stockholder acquired shares;

• the interested stockholder acquired at least 85% of the voting stock of the corporation in the transaction in which it became an interested stockholder; or

• the business combination is approved by a majority of the board of directors and by the affirmative vote of two-thirds of the outstanding voting stock owned by disinterested stockholders at an annual or special meeting.

A business combination is defined broadly to include mergers, consolidations, sales or other dispositions of assets having an aggregate value of 10% or more of the consolidated assets of the corporation, and certain transactions that would increase the interested stockholder’s proportionate share ownership in the corporation. In general, Section 203 defines an interested stockholder as an entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person affiliated with or controlling or controlled by such entity or person.

Exclusive Forum

The By-laws provide that, unless we consent in writing to the selection of an alternative forum, the sole and exclusive forum for (a) any derivative action or proceeding brought on behalf of us, (b) any action asserting a claim of breach of a fiduciary duty owed by any of our current or past directors, officers or other employees to us or any of our stockholders (including any beneficial owner of our stock), (c) any action asserting a claim arising pursuant to any provision of the DGCL, the Charter or the By-Laws and (d) any action asserting a claim governed by the internal affairs doctrine, will, to the fullest extent permitted by law, be the Court of Chancery of the State of Delaware or, if such court lacks jurisdiction, any state or federal court in the state of Delaware that has jurisdiction. The By-laws also provide that any person (including any entity) purchasing or otherwise acquiring or holding any interest in shares of our capital stock will be deemed to have notice of and consented to the exclusive forum provisions in the By-laws.

Limitations of Directors’ Liability

The Charter provides that none of our directors will be personally liable to us or our stockholders for monetary damages for breach of fiduciary duty as a director, except for liability:

• for any breach of the director’s duty of loyalty to us or our stockholders;

• for acts of omissions not in good faith or which involve intentional misconduct or a knowing violation of law;

• under Section 174 of the DGCL; or

• for any transaction from which the director derived an improper personal benefit.

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The effect of these provisions is to eliminate our rights and the rights of our stockholders (through stockholders’ derivatives suits on behalf of us) to recover monetary damages against a director for breach of fiduciary duty as a director (including breaches resulting from grossly negligent behavior), except in the situations described above. These provisions do not limit the liability of directors under federal securities laws and do not affect the availability of equitable remedies such as an injunction or rescission based upon a director’s breach of his duty of care.

Ownership Limitations and Transfer Restrictions

To facilitate our continued qualification as a real estate investment trust (“REIT”) under the Internal Revenue Code of 1986, as amended (“Code”), the Charter contains ownership limitations and transfer restrictions on our capital stock. These ownership limitations and transfer restrictions could have the effect of delaying, deferring or preventing a transaction or a change in control of us that might involve a premium price for our capital stock or otherwise be in the best interest of our stockholders. All certificates representing shares of capital stock bear a legend describing such ownership limitations and transfer restrictions.

In order for us to continue to satisfy the requirements for REIT qualification, our capital stock must be beneficially owned by 100 or more persons during at least 335 days of a taxable year of 12 months or during a proportionate part of a shorter taxable year. Also, not more than 50% of the value of the outstanding shares of our capital stock may be owned, directly or indirectly, by five or fewer “individuals” (as defined in the Code to include certain entities such as private foundations) during the last half of a taxable year. To satisfy these ownership requirements and other requirements for continued qualification as a REIT and to otherwise protect us from the consequences of a concentration of ownership among our stockholders, the Charter contains provisions limiting the ownership and restricting the transfer of shares of our capital stock.

The relevant section of the Charter provides that, among other things and subject to certain exceptions described below, no “Person” (as defined in the Charter) may beneficially or constructively own, or be deemed to beneficially or constructively own by virtue of the attribution provisions of the Code, more than 9.8%, by value or number of shares, whichever is more restrictive, of the outstanding shares of our common stock (which restriction we refer to as the “common stock ownership limit”), or 9.8% in aggregate value of the outstanding shares of all classes and series of our capital stock, including our common stock and Mandatory Convertible Preferred Stock (which restriction we refer to as the “aggregate stock ownership limit”).

The applicable constructive ownership rules under the Code are complex and may cause capital stock owned actually or constructively by a group of related individuals or entities to be treated as owned by one individual or entity. As a result, the acquisition of less than 9.8% in value of our outstanding capital stock or less than 9.8% in value or number of our outstanding shares of common stock (including through the acquisition of an interest in an entity that owns, actually or constructively, our common stock) by an individual or entity could nevertheless cause that individual or entity, or another individual or entity, to own, constructively or beneficially, in excess of 9.8% in value of our outstanding capital stock or 9.8% in value or number of our outstanding shares of common stock. The number and value of our outstanding shares of capital stock (or any class or series thereof) beneficially or constructively owned by any individual or entity shall be determined by our board of directors, whose determination shall be binding and conclusive.

Our board of directors, in its sole discretion, may (prospectively or retroactively) exempt a person from the aggregate stock ownership limit and common stock ownership limit described above and may establish different limits on ownership for any such person (which we refer to as an “excepted holder limit”) and may (prospectively or retroactively) increase any excepted holder limit with respect to any person. However, our board of directors may not exempt any person or increase an excepted holder limit for any person whose ownership of outstanding capital stock would violate the other provisions on transferability and ownership set forth in the Charter and described below. In order to be considered by our board of directors for an exemption from the aggregate stock ownership limit and common stock ownership limit or for an increase in an excepted

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holder limit, a person must make such representations and undertakings as our board of directors determines are reasonably necessary to determine that no person’s beneficial or constructive ownership of our capital stock will violate the other provisions on transferability and ownership set forth in the Charter and described below, and that such person does not and will not own, actually or constructively, an interest in a tenant of ours that would cause us to own, actually or constructively, more than a 9.9% interest in such tenant. As a condition to such exemption or such increase in an excepted holder limit, our board of directors may require an opinion of counsel or Internal Revenue Service ruling satisfactory to our board of directors and may impose such other conditions or restrictions as it deems necessary, appropriate or desirable in connection with granting such exemption or such increase in an excepted holder limit.

Our board of directors, in its sole discretion, may also increase or decrease the aggregate stock ownership limit and common stock ownership limit for all stockholders, provided that the new ownership limits would not allow five or fewer persons to beneficially own more than 49.9% of the value of our outstanding capital stock. A reduced aggregate stock ownership limit and common stock ownership limit will not apply to any person whose percentage ownership of our capital stock or our common stock, as applicable, is in excess of such decreased ownership limit, until such time as such person’s percentage ownership of our capital stock or our common stock, as applicable, equals or falls below such decreased ownership limit. However, until such time as such person’s percentage ownership of our capital stock or our common stock, as applicable, falls below such decreased ownership limit any further acquisition of our capital stock or our common stock, as applicable, will be in violation of the decreased ownership limit.

The Charter further prohibits:

• any person from beneficially owning shares of our capital stock to the extent that such beneficial ownership would result in our being “closely held” within the meaning of Section 856(h) of the Code (without regard to whether the ownership interest is held during the last half of a taxable year);

• any person from beneficially or constructively owning shares of our capital stock to the extent that such beneficial or constructive ownership would otherwise result in our failing to qualify as a REIT (including, but not limited to, beneficial ownership or constructive ownership that would result in our actually owning or constructively owning an interest in a tenant that is described in Section 856(d)(2)(B) of the Code if the income derived by us from such tenant would cause us to fail to satisfy any of the gross income requirements of Section 856(c) of the Code);

• any person from beneficially or constructively owning shares of our capital stock to the extent such beneficial or constructive ownership could result in our failing to qualify as a “domestically controlled qualified investment entity” within the meaning of Section 897(h)(4)(B) of the Code; and

• any person from transferring shares of our capital stock if such transfer would result in shares of our capital stock being beneficially owned by fewer than 100 persons (determined under the principles of Section 856(a)(5) of the Code).

The foregoing provisions on transferability and ownership, including the aggregate stock ownership limit and common stock ownership limit, will not apply if our board of directors determines that it is no longer in our best interests to continue to qualify as a REIT.

Any person who acquires or attempts or intends to acquire beneficial or constructive ownership of shares of our capital stock that will or may violate the aggregate stock ownership limit and common stock ownership limit or any of the other foregoing restrictions on transferability and ownership will be required to give written notice to us immediately (or, in the case of a proposed or attempted transaction, written notice at least 15 days prior to such transaction) and provide us with such other information as we may request in order to determine the effect, if any, of such transfer on our status as a REIT and to ensure compliance with the aggregate stock ownership limit and common stock ownership limit.

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Pursuant to the Charter, if there is any purported transfer of our capital stock or other event or change of circumstances that, if effective, would violate any of the restrictions described above, then the number of shares causing the violation (rounded up to the nearest whole share) will be automatically transferred to a trust for the exclusive benefit of a designated charitable beneficiary, except that any transfer that results in the violation of the restriction relating to our capital stock being beneficially owned by fewer than 100 persons will be automatically void and of no force or effect. The automatic transfer will be effective as of the close of business on the business day prior to the date of the purported transfer or other event or change of circumstances that requires the transfer to the trust. We refer below to the person that would have owned the shares if they had not been transferred to the trust as the “purported transferee.” No purported transferee shall acquire any rights in such shares and any dividend or other distribution paid to the purported transferee, prior to our discovery that the shares had been automatically transferred to a trust as described above, must be repaid to the trustee upon demand. If the transfer to the trust as described above is not automatically effective, for any reason, to prevent violation of the applicable restriction contained in the Charter, then the transfer of the excess shares will be automatically void and of no force or effect.

Shares of our capital stock transferred to the trustee are deemed to be offered for sale to us or our designee at a price per share equal to the lesser of (i) the price per share paid by the purported transferee for the shares or, if the purported transferee did not give value for the shares in connection with the event causing the shares to be held in trust (e.g., in the case of a gift, devise or other such transaction), the market price on the day of such event and (ii) the market price of the shares on the date we accept, or our designee accepts, such offer. We have the right to accept such offer until the trustee has sold the shares of our capital stock held in the trust pursuant to the clauses discussed below. We may reduce the amount payable to the purported transferee by the amount of dividends or other distributions that we paid to the purported transferee prior to our discovery that the shares had been transferred to the trust and that is owed by the purported transferee to the trustee as described above. We shall pay the amount of such reduction to the trustee for the benefit of the charitable beneficiary. Upon a sale to us, the interest of the charitable beneficiary in the shares sold terminates and the trustee must distribute the net proceeds of the sale to the purported transferee and any dividends or other distributions held by the trustee shall be paid to the charitable beneficiary.

If we do not buy the shares, the trustee must, within 20 days after receiving notice from us of the transfer of shares to the trust, sell the shares to a person or entity who could own the shares without violating the restrictions described above. Upon such a sale, the trustee must distribute to the purported transferee an amount equal to the lesser of (i) the price paid by the purported transferee for the shares or, if the purported transferee did not give value for the shares in connection with the event causing the shares to be held in trust (e.g., in the case of a gift, devise or other such transaction), the market price of the shares on the day of the event causing the shares to be held in the trust and (ii) the sales proceeds (net of commissions and other expenses of sale) received by the trustee for the shares. The trustee may reduce the amount payable to the purported transferee by the amount of any dividends or other distributions that we paid to the purported transferee before our discovery that the shares had been transferred to the trust and that is owed by the purported transferee to the trustee as described above. Any net sales proceeds in excess of the amount payable to the purported transferee will be immediately paid to the charitable beneficiary, together with any dividends or other distributions held by the trustee with respect to such capital stock. In addition, if prior to discovery by us that shares of our capital stock have been transferred to a trust, such shares of capital stock are sold by a purported transferee, then such shares will be deemed to have been sold on behalf of the trust and, to the extent that the purported transferee received an amount for or in respect of such shares that exceeds the amount that such purported transferee was entitled to receive as described above, such excess amount shall be paid to the trustee upon demand and immediately paid to the charitable beneficiary. The purported transferee will have no rights in the shares held by the trustee.

The trustee will be designated by us and must be unaffiliated with us and with any purported transferee. Prior to the sale of any shares by the trust, the trustee will receive, in trust for the beneficiary, all dividends and other distributions paid by us with respect to the shares, and may also exercise all voting rights with respect to the shares.

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Subject to the DGCL, effective as of the date that the shares have been transferred to the trust, the trustee will have the authority, at the trustee’s sole discretion:

• to rescind as void any vote cast by a purported transferee prior to our discovery that the shares have been transferred to the trust; and

• to recast the vote in accordance with the desires of the trustee acting for the benefit of the charitable beneficiary of the trust.

However, if we have already taken irreversible corporate action, then the trustee may not rescind and recast the vote.

In addition, if our board of directors determines that a proposed or purported transfer would violate the restrictions on ownership and transfer of our capital stock set forth in the Charter, our board of directors may take such action as it deems necessary, appropriate or desirable to refuse to give effect to or to prevent such violation, including causing us to redeem shares of our capital stock, refusing to give effect to the transfer on our books or instituting proceedings to enjoin the transfer.

Within 30 days after the end of each taxable year, every owner of more than 5% (or such lower percentage as required by the Code or the Treasury regulations thereunder) of the outstanding shares of our capital stock must provide us written notice of the person’s name and address, the number of shares of each class and series of our capital stock that such person beneficially or constructively owns and a description of the manner in which the shares are held. Each such owner must also provide us with such additional information as we may request in order to determine the effect, if any, of such owner’s beneficial or constructive ownership on our qualification as a REIT and to ensure compliance with the aggregate stock ownership limit and common stock ownership limit. In addition, each beneficial or constructive owner of our capital stock, and any person (including the stockholder of record) who is holding shares of our capital stock for a beneficial or constructive owner will, upon demand, be required to provide us with such information as we may request in order to determine our qualification as a REIT and to comply with the requirements of any taxing authority or governmental authority or to determine such compliance and to ensure compliance with the aggregate stock ownership limit and common stock ownership limit.

Transfer Agent and Registrar

Computershare Inc. is the transfer agent and registrar for the Company’s common stock and the conversion agent for the Mandatory Convertible Preferred Stock.

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DESCRIPTION OF WARRANTS

We may issue warrants for the purchase of debt securities, preferred stock or common stock. Warrants may be issued independently or together with debt securities, preferred stock or common stock offered by any prospectus supplement and may be attached to or separate from any such offered securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and a bank or trust company, as warrant agent. The warrant agent will act solely as our agent in connection with the warrants and will not assume any obligation or relationship of agency or trust for or with any holders or beneficial owners of warrants. The following summary of certain provisions of the warrants does not purport to be complete and is subject to, and qualified in its entirety by reference to, the provisions of the warrant agreement that will be filed with the SEC in connection with the offering of such warrants.

The prospectus supplement relating to a particular issue of warrants will describe the terms of such warrants, including the following:

• the title of such warrants;

• the offering price for such warrants, if any;

• the aggregate number of such warrants;

• the designation and terms of the securities purchasable upon exercise of such warrants;

• if applicable, the designation and terms of the securities with which such warrants are issued and the number of such warrants issued with each such security;

• if applicable, the date from and after which such warrants and any securities issued therewith will be separately transferable;

• the principal amount of debt securities purchasable upon exercise of a warrant and the price at which such principal amount of debt securities may be purchased upon exercise (which price may be payable in cash, securities, or other property) and the number of shares of common stock or preferred stock purchasable upon exercise of a warrant and the price at which such shares may be purchased upon exercise;

• the date on which the right to exercise such warrants shall commence and the date on which such right shall expire;

• if applicable, the minimum or maximum amount of such warrants that may be exercised at any one time;

• information with respect to book-entry procedures, if any;

• the currency or currency units in which the offering price, if any, and the exercise price are payable;

• if applicable, a discussion of material U.S. federal income tax considerations;

• the antidilution provisions of such warrants, if any;

• the redemption or call provisions, if any, applicable to such warrants; and

• any additional terms of such warrants, including terms, procedures, and limitations relating to the exchange and exercise of such warrants.

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PLAN OF DISTRIBUTION

We and any selling security holder may offer and sell the securities covered by this prospectus from time to time, in one or more transactions, at market prices prevailing at the time of sale, at prices related to market prices, at a fixed price or prices subject to change, at varying prices determined at the time of sale or at negotiated prices, by a variety of methods, including the following:

• through agents;

• to or through underwriters;

• in “at the market offerings,” within the meaning of Rule 415(a)(4) under the Securities Act, to or through a market maker or into an existing trading market, on an exchange or otherwise;

• through brokers or dealers;

• directly by us or any selling security holders to purchasers, including through a specific bidding, auction or other process; or

• through a combination of any of these methods of sale.

Registration of the securities covered by this prospectus does not mean that those securities necessarily will be offered or sold.

In effecting sales, brokers or dealers engaged by us may arrange for other brokers or dealers to participate. Broker-dealer transactions may include:

• purchases of the securities by a broker-dealer as principal and resales of the securities by the broker-dealer for its account pursuant to this prospectus;

• ordinary brokerage transactions; or

• transactions in which the broker-dealer solicits purchasers.

In addition, we and any selling security holder may sell any securities covered by this prospectus in private transactions or under Rule 144 of the Securities Act rather than pursuant to this prospectus.

We may sell offered securities through agents designated by us from time to time. Any agent in the offer or sale of the securities for which this prospectus is delivered will be named, and any commissions payable by us to that agent will be set forth, in the applicable prospectus supplement. Unless indicated in such prospectus supplement, the agents will have agreed to use their reasonable best efforts to solicit purchases for the period of their appointment.

In connection with the sale of securities covered by this prospectus, broker-dealers may receive commissions or other compensation from us in the form of commissions, discounts or concessions. Broker-dealers may also receive compensation from purchasers of the securities for whom they act as agents or to whom they sell as principals or both. Compensation as to a particular broker-dealer may be in excess of customary commissions or in amounts to be negotiated. In connection with any underwritten offering, underwriters may receive compensation in the form of discounts, concessions or commissions from us or from purchasers of the securities for whom they act as agents. Underwriters may sell the securities to or through dealers, and such dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for whom they may act as agents. Any underwriters, broker-dealers agents or other persons acting on our behalf that participate in the distribution of the securities may be deemed to be “underwriters” within the meaning of the Securities Act, and any profit on the sale of the securities by them and any discounts, commissions or concessions received by any of those underwriters, broker-dealers agents or other persons may be deemed to be underwriting discounts and commissions under the Securities Act.

In connection with the distribution of the securities covered by this prospectus or otherwise, we or any selling stockholder may enter into hedging transactions with broker-dealers or other financial institutions. In

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connection with such transactions, broker-dealers or other financial institutions may engage in short sales of our securities in the course of hedging the positions they assume with us or any selling stockholder. We or any selling stockholder may also sell securities short and deliver the securities offered by this prospectus to close out our short positions. We or any selling security holder may also enter into option or other transactions with broker-dealers or other financial institutions, which require the delivery to such broker-dealer or other financial institution of securities offered by this prospectus, which securities such broker-dealer or other financial institution may resell pursuant to this prospectus, as supplemented or amended to reflect such transaction. We or any selling security holder may also from time to time pledge our securities pursuant to the margin provisions of our customer agreements with our brokers. Upon our default, the broker may offer and sell such pledged securities from time to time pursuant to this prospectus, as supplemented or amended to reflect such transaction.

At any time a particular offer of the securities covered by this prospectus is made, a revised prospectus or prospectus supplement, if required, will be distributed which will set forth the aggregate amount of securities covered by this prospectus being offered and the terms of the offering, including the name or names of any underwriters, dealers, brokers or agents, any discounts, commissions, concessions and other items constituting compensation from us and any discounts, commissions or concessions allowed or reallowed or paid to dealers. Such prospectus supplement, and, if necessary, a post-effective amendment to the registration statement of which this prospectus forms a part, will be filed with the SEC to reflect the disclosure of additional information with respect to the distribution of the securities covered by this prospectus. In order to comply with the securities laws of certain states, if applicable, the securities sold under this prospectus may only be sold through registered or licensed broker-dealers. In addition, in some states the securities may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from registration or qualification requirements is available and is satisfied.

In connection with an underwritten offering, we and any selling stockholder would execute an underwriting agreement with an underwriter or underwriters. Unless otherwise indicated in the revised prospectus or applicable prospectus supplement, such underwriting agreement would provide that the obligations of the underwriter or underwriters are subject to certain conditions precedent, and that the underwriter or underwriters with respect to a sale of the covered securities will be obligated to purchase all of the covered securities, if any such securities are purchased. We or any selling security holder may grant to the underwriter or underwriters an option to purchase additional securities at the public offering price, less any underwriting discount, as may be set forth in the revised prospectus or applicable prospectus supplement. If we or any selling security holder grants any such option, the terms of that option will be set forth in the revised prospectus or applicable prospectus supplement.

To the extent that we make sales through one or more underwriters or agents in at the market offerings, we will do so pursuant to the terms of a sales agency financing agreement or other at the market offering arrangement between us and the underwriters or agents. If we engage in at the market sales pursuant to any such agreement, we will issue and sell our securities through one or more underwriters or agents, which may act on an agency basis or on a principal basis. During the term of any such agreement, we may sell securities on a daily basis in exchange transactions or otherwise as we agree with the underwriters or agents. The agreement will provide that any securities sold will be sold at prices related to the then prevailing market prices for our securities. Therefore, exact figures regarding proceeds that will be raised or commissions to be paid cannot be determined as of the date of this prospectus. Pursuant to the terms of the agreement, we may agree to sell, and the relevant underwriters or agents may agree to solicit offers to purchase, blocks of our common stock or other securities. The terms of each such agreement will be set forth in more detail in a prospectus supplement.

Underwriters, agents, brokers or dealers may be entitled, pursuant to relevant agreements entered into with us, to indemnification by us or any selling security holder against certain civil liabilities, including liabilities under the Securities Act that may arise from any untrue statement or alleged untrue statement of a material fact, or any omission or alleged omission to state a material fact in this prospectus, any supplement or amendment hereto, or in the registration statement of which this prospectus forms a part, or to contribution with respect to payments which the underwriters, agents, brokers or dealers may be required to make.

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LEGAL MATTERS

The validity of the securities offered in this prospectus and any related prospectus supplement and certain legal matters will be passed upon for us by Cravath, Swaine & Moore LLP, New York, New York. If the securities are being distributed in an underwritten offering, certain legal matters will be passed upon for the underwriters by counsel identified in the related prospectus supplement.

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EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control over Financial Reporting), incorporated in this prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2017, have been so incorporated in reliance on the report (which contains an explanatory paragraph on the effectiveness of internal control over financial reporting due to the exclusion of certain elements of the internal control over financial reporting of the FiberNet, Wilcon and Lightower businesses the registrant acquired during 2017) of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The financial statements of LTS Group Holdings LLC and its subsidiary as of and for the year ended December 31, 2016, incorporated in this prospectus by reference to our Current Report on Form 8-K/A filed December 15, 2017 (which amended our Current Report on Form 8-K filed November 1, 2017), have been audited by Deloitte & Touche LLP, independent auditors, as stated in their report, which is incorporated herein by reference. Such financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the internet at the SEC’s website at http://www.sec.gov. You may also read and copy any document we file with the SEC at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room. Our SEC filings are also available through the investor relations section of our website at http://investor.crowncastle.com. Except for documents incorporated by reference into this prospectus as described below, no information in, or that can be accessed through, our website is incorporated by reference into this prospectus, and no such information should be considered as part of this prospectus.

We are “incorporating by reference” into this prospectus specific documents that we file with the SEC, which means that we can disclose important information to you by referring you to those documents that are considered part of this prospectus. Information that we file subsequently with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below, and any future documents that we file with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act until the termination of the offerings of all of the securities covered by this prospectus (other than information furnished under Items 2.02 or 7.01 of any Form 8-K or Rule 406T of Regulation S-T, which is not deemed filed under the Exchange Act). This prospectus is part of a registration statement filed with the SEC.

We are “incorporating by reference” into this prospectus the following documents filed with the SEC (excluding any portions of such documents that have been “furnished” but not “filed” for purposes of the Exchange Act):

• our Annual Report on Form 10-K for the fiscal year ended December 31, 2017;

• our Current Reports on Form 8-K filed January 10, 2018, January 17, 2018, February 27, 2018, March 5, 2018 and March 26, 2018 and our Current Report on Form 8-K/A filed February 21, 2018 (which amended our Current Report on Form 8-K filed November 2, 2017);

• our Current Report on Form 8-K/A filed December 15, 2017 (which amended our Current Report on Form 8-K filed November 1, 2017); and

• the description of our capital stock contained in Exhibit 4.1 of our Current Report on Form 8-K filed December 16, 2014, as supplemented by the description of our Mandatory Convertible Preferred Stock

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contained in our Final Prospectus Supplement filed pursuant to Rule 424(b)(2) under the Securities Act on July 24, 2017 and any subsequent amendments and reports filed for the purpose of updating such descriptions (collectively, “Capital Stock Description”).

We will provide to each person, including any beneficial owner of our securities, to whom a prospectus is delivered, upon written or oral request and without charge, a copy of the documents referred to above that we have incorporated by reference in this prospectus. You can request copies of such documents if you write or call us at the following address or telephone number: Investor Relations, Crown Castle International Corp., 1220 Augusta Drive, Suite 600, Houston, Texas 77057, (713) 570-3000, or you may visit the investor relations section of our website at http://investor.crowncastle.com for copies of any such document. Except as expressly stated herein, no information contained in, or that can be accessed through, our website is incorporated by reference into this prospectus, and no such information should be considered a part of this prospectus.

This prospectus, any accompanying prospectus supplement or information incorporated by reference herein or therein contains summaries of certain agreements that we have filed as exhibits to various SEC filings, as well as certain agreements that we will enter into in connection with the offering of securities covered by any particular accompanying prospectus supplement. The descriptions of these agreements contained in this prospectus, any accompanying prospectus supplement or information incorporated by reference herein or therein do not purport to be complete and are subject to, and qualified in their entirety by reference to, the definitive agreements. Copies of the definitive agreements will be made available without charge to you by making a written or oral request to us.

Any statement contained herein or in a document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained herein, in any other subsequently filed document which also is or is deemed to be incorporated by reference herein or in any accompanying prospectus supplement, modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified and superseded, to constitute a part of this prospectus.

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$750,000,000

Crown Castle International Corp.

Prospectus Supplement

April 6, 2018

BofA Merrill Lynch	Barclays	Citigroup	Credit Agricole CIB
Fifth Third Securities	Jefferies	J.P. Morgan	Mizuho Securities
Morgan Stanley	MUFG	RBC Capital Markets	SOCIETE GENERALE
SMBC Nikko	SunTrust Robinson Humphrey	TD Securities	Wells Fargo Securities