BlackRock Capital Appreciation Fund, Inc.

BlackRock Municipal Bond Fund, Inc.

BlackRock National Municipal Fund

(each, a “Fund” and together, the “Funds”)

Supplement dated May 17, 2016 to the Prospectus of each Fund

Effective on August 15, 2016, as specified below, all of the issued and outstanding BlackRock Shares of each Fund will be redesignated as Class K Shares. The redesignation to Class K Shares is expected to have no impact on, or result in a decrease in, total operating expenses of the class. Shareholders will continue to receive all of the same services and have all of the same rights and privileges that they currently have as holders of BlackRock Shares.

Effective on August 15, 2016, all references to BlackRock Shares in each Fund’s current Prospectus are replaced with Class K Shares unless otherwise described below.

The section entitled “Fund Overview—Purchase and Sale of Fund Shares” in each Fund’s current Prospectus for BlackRock Shares is deleted in its entirety and replaced with the following:

Class K Shares of the Fund are available only to (i) employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs and SARSEPs) (“Employer-Sponsored Retirement Plans”), (ii) collective trust funds, investment companies and other pooled investment vehicles, each of which may purchase shares of the Fund through a Financial Intermediary (as defined below) that has entered into an agreement with the Fund’s distributor to purchase such shares, (iii) “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, local, city, and state governmental institutions, corporations and insurance company separate accounts, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares and (iv) any other investors who met the eligibility criteria for BlackRock Shares or Class K Shares prior to August 15, 2016 and have continually held Class K Shares of the Fund in the same account since August 15, 2016.

You may purchase or redeem shares of the Fund each day the New York Stock Exchange is open. Purchase orders may also be placed by calling (800) 537-4942, by mail (c/o BlackRock, P.O. Box 9819, Providence, Rhode Island 02940-8019), or online at www.blackrock.com. Institutional Investors are subject to a $5 million minimum initial investment requirement. Other investors, including Employer-Sponsored Retirement Plans, have no minimum initial investment requirement. There is no minimum investment amount for additional purchases.

The section entitled “Fund Overview—Tax Information” in each Fund’s current Prospectus for BlackRock Shares is deleted in its entirety and replaced with the following:

Different income tax rules apply depending on whether you are invested through a qualified plan exempt from tax under section 401(a) of the Internal Revenue Code of 1986, as amended. If you are invested through such a plan (and Fund shares are not “debt-financed property” to the plan), then the dividends paid by the Fund and the gain realized from a redemption or exchange of Fund shares will generally not be subject to Federal income taxes until you withdraw or receive distributions from the plan. If you are not invested through such a plan, then the Fund’s dividends and gain from a redemption or exchange may be subject to Federal income taxes and may be taxed as ordinary income or capital gains, unless you are a tax-exempt investor.

The section entitled “Account Information—How to Choose the Share Class that Best Suits Your Needs” in each Fund’s current Prospectus for BlackRock Shares is deleted in its entirety, renamed “Account Information—Details About the Share Class” and replaced with the following:

The Fund currently offers multiple share classes (Class K Shares in this prospectus), each with its own sales charge and expense structure, allowing you to invest in the way that best suits your needs. Each share class represents an ownership interest in the same investment portfolio of the Fund. When you choose your class of shares, you should consider the size of your investment and how long you plan to hold your shares. Only certain investors are eligible to buy Class K Shares. Either your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock, The PNC Financial

Services Group, Inc. (“PNC”) and their respective affiliates) (each a “Financial Intermediary”) can help you determine whether you are eligible to buy Class K Shares.

The Fund’s shares are distributed by BlackRock Investments, LLC (the “Distributor”), an affiliate of BlackRock.

The table below summarizes key features of Class K Shares of the Fund.

Class K Shares at a Glance

	Class K Shares
Availability	Available only to (i) employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs and SARSEPs) (“Employer-Sponsored Retirement Plans”), (ii) collective trust funds, investment companies and other pooled investment vehicles, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares, (iii) “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, local, city, and state governmental institutions, corporations and insurance company separate accounts, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Distributor to purchase such shares and (iv) any other investors who met the eligibility criteria for BlackRock Shares or Class K Shares prior to August 15, 2016 and have continually held Class K Shares of the Fund in the same account since August 15, 2016.
Minimum Investment	There is no minimum initial investment requirement for any Employer-Sponsored Retirement Plans or any other eligible investors other than Institutional Investors. $5 million minimum initial investment for Institutional Investors. There is no minimum investment amount for additional purchases.
Initial Sales Charge?	No. Entire purchase price is invested in shares of the Fund.
Deferred Sales Charge?	No.
Distribution and Service (12b-1) Fees?	No.
Redemption Fees?	No.

The Fund reserves the right to modify or waive the above-stated policies at any time.

When Class K Shares are purchased through a customer’s account in an Employer-Sponsored Retirement Plan through procedures established by the Employer-Sponsored Retirement Plan, confirmation of share purchases and redemptions will be sent to the Employer-Sponsored Retirement Plan. A customer’s ownership of shares will be recorded by the Employer-Sponsored Retirement Plan and reflected in the account statements provided by the Employer-Sponsored Retirement Plan to its participants.

If you purchased your shares through an Employer-Sponsored Retirement Plan and you transfer your investment from an Employer-Sponsored Retirement Plan to a type of account, such as an individual retirement account, that is not an eligible Class K Share investor in the Fund, you must liquidate your investment in Class K Shares of the Fund and purchase a share class of another fund advised by BlackRock or its affiliates that is available for purchase by that type of account.

For investors not purchasing shares through an Employer-Sponsored Retirement Plan, please see below for information on how to buy, sell and transfer shares.

The section entitled “Account Information—Distribution and Service Payments” in each Fund’s current Prospectus for BlackRock Shares is deleted in its entirety.

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The section entitled “Account Information—How to Buy, Sell and Transfer Shares” in each Fund’s current Prospectus for BlackRock Shares is deleted in its entirety and replaced with the following:

The chart on the following pages summarizes how to buy, sell and transfer shares through your Financial Intermediary. If you are not purchasing shares through an Employer-Sponsored Retirement Plan, you may also buy, sell and transfer shares through BlackRock, if your account is held directly with BlackRock. To learn more about buying, selling or transferring shares through BlackRock, call (800) 537-4942. Because the selection of a mutual fund involves many considerations, your Financial Intermediary may help you with this decision.

With certain limited exceptions, the Fund is generally available only to investors residing in the United States and may not be distributed by a foreign Financial Intermediary. Under this policy, in order to accept new accounts or additional investments (including by way of exchange from another mutual fund sponsored and advised by BlackRock or its affiliates) into existing accounts, the Fund generally requires that (i) a shareholder that is a natural person be a U.S. citizen or resident alien, in each case residing within the United States or a U.S. territory (including APO/FPO/DPO addresses), and have a valid U.S. taxpayer identification number, and (ii) a Financial Intermediary or a shareholder that is an entity be domiciled in the United States and have a valid U.S. taxpayer identification number or be domiciled in a U.S. territory and have a valid U.S. taxpayer identification number or IRS Form W-8. Any existing account that is updated to reflect a non-U.S. address will also be restricted from making additional investments.

The Fund may reject any purchase order, modify or waive the minimum initial or subsequent investment requirements for any shareholders and suspend and resume the sale of any share class of the Fund at any time for any reason. In addition, the Fund may waive certain requirements regarding the purchase, sale or transfer of shares described below.

Under certain circumstances, if no activity occurs in an account within a time period specified by state law, a shareholder’s shares in the Fund may be transferred to that state.

How to Buy Shares

	Your Choices	Important Information for You to Know
Initial Purchase	Determine the amount of your investment	There is no minimum initial investment for any Employer-Sponsored Retirement Plans or any other investors other than Institutional Investors. For Institutional Investors, there is a $5 million minimum investment for all accounts.
	Have your Financial Intermediary submit your purchase order	The price of your shares is based on the next calculation of the Fund’s net asset value after your order is placed. Any purchase orders placed prior to the close of business on the New York Stock Exchange (the “NYSE”) (generally 4:00 p.m. Eastern time) will be priced at the net asset value determined that day. Certain Financial Intermediaries, however, may require submission of orders prior to that time. Purchase orders placed after that time will be priced at the net asset value determined on the next business day. A broker-dealer or financial institution maintaining the account in which you hold shares may charge a separate account, service or transaction fee on the purchase or sale of Fund shares that would be in addition to the fees and expenses shown in the Fund’s “Fees and Expenses” table. The Fund may reject any order to buy shares and may suspend the sale of shares at any time. Certain Financial Intermediaries may charge a processing fee to confirm a purchase.

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	Your Choices	Important Information for You to Know
Initial Purchase (continued)	Or contact BlackRock (for accounts held directly with BlackRock)	For investors not purchasing shares through an Employer-Sponsored Retirement Plan, to purchase shares directly from BlackRock, call (800) 537-4942 and request a new account application.
Add to Your Investment	Purchase additional shares	There is no minimum investment amount for additional purchases.
	Have your Financial Intermediary submit your purchase order for additional shares	To purchase additional shares, you may contact your Financial Intermediary or Employer-Sponsored Retirement Plan.
	Or contact BlackRock (for accounts held directly with BlackRock)	For investors not purchasing shares through an Employer-Sponsored Retirement Plan: Purchase by Telephone: Call the Fund at (800) 537-4942 and speak with one of our representatives. The Fund has the right to reject any telephone request for any reason. Purchase by Internet: You may purchase your shares, and view activity in your account, by logging onto the BlackRock website at www.blackrock.com. Purchases made on the Internet using the Automated Clearing House (“ACH”) will have a trade date that is the day after the purchase is made. Certain institutional clients’ purchase orders placed by wire prior to the close of business on the NYSE will be priced at the net asset value determined that day. Contact your Financial Intermediary or BlackRock for further information. Limits on amounts that may be purchased via Internet may vary. For additional information call BlackRock at (800) 537-4942. Please read the On-Line Services Disclosure Statement and User Agreement, the Terms and Conditions page and the Consent to Electronic Delivery Agreement (if you consent to electronic delivery), before attempting to transact online. The Fund employs reasonable procedures to confirm that transactions entered over the Internet are genuine. By entering into the User Agreement with the Fund in order to open an account through the website, the shareholder waives any right to reclaim any losses from the Fund or any of its affiliates, incurred through fraudulent activity.
	Acquire additional shares by reinvesting dividends and capital gains	All dividends and capital gains distributions are automatically reinvested without a sales charge. To make any changes to your dividend and/or capital gains distributions options, please call BlackRock at (800) 537-4942 (for investors who are not purchasing shares through an Employer-Sponsored Retirement Plan) or contact your Financial Intermediary.

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	Your Choices	Important Information for You to Know
How to Pay for Shares	Making payment for purchases	If you are purchasing shares through an Employer-Sponsored Retirement Plan, payment for an order must be made in Federal funds or other immediately available funds by the time specified by your Financial Intermediary, but in no event later than 4:00 p.m. (Eastern time) on the first business day following the receipt of the order. If payment is not received by this time, the order will be canceled and you and your Financial Intermediary will be responsible for any loss to the Fund. If you are not purchasing shares through an Employer-Sponsored Retirement Plan, payment for shares must normally be made in Federal funds or other immediately available funds by the time specified by your Financial Intermediary but in no event later than 4:00 p.m. (Eastern time) on the first business day following the receipt of the order. Payment may also, at the discretion of the Fund, be made in the form of securities that are permissible investments for the respective fund. If payment is not received by this time, the order will be canceled and you and your Financial Intermediary will be responsible for any loss to the Fund.

How to Sell Shares

	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares	Have your Financial Intermediary submit your sales order	If you purchased shares through an Employer-Sponsored Retirement Plan, you can make redemption requests through your Financial Intermediary in accordance with the procedures applicable to your accounts. These procedures may vary according to the type of account and the Financial Intermediary involved, and customers should consult their Financial Intermediary in this regard. Financial Intermediaries are responsible for transmitting redemption orders and crediting their customers’ accounts with redemption proceeds on a timely basis. Information relating to such redemption services and charges to process a redemption of shares, if any, should be obtained by customers from their Financial Intermediaries. The price of Class K Shares is based on the next calculation of the Fund’s net asset value after your order is placed. For your redemption request to be priced at the net asset value on the day of your request, you must submit your request to your Financial Intermediary prior to that day’s close of business on the NYSE (generally 4:00 p.m. Eastern time). Certain Financial Intermediaries, however, may require submission of orders prior to that time. Any redemption request placed after that time will be priced at the net asset value at the close of business on the next business day. Certain Financial Intermediaries may charge a fee to process a redemption of shares. The Fund may reject an order to sell shares under certain circumstances.

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	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares (continued)	Have your Financial Intermediary submit your sales order (continued)	If you did not purchase your shares through an Employer-Sponsored Retirement Plan, you can make redemption requests through your Financial Intermediary. The price of your shares is based on the next calculation of net asset value after your order is placed. For your redemption request to be priced at the net asset value on the day of your request, you must submit your request to your Financial Intermediary prior to that day’s close of business on the NYSE (generally 4:00 p.m. (Eastern time)). Certain Financial Intermediaries, however, may require submission of orders prior to that time. Any redemption request placed after that time will be priced at the net asset value at the close of business on the next business day. The Fund may reject an order to sell shares under certain circumstances.
	Selling shares held directly with BlackRock	Methods of Redeeming if You Did Not Purchase Your Shares Through an Employer-Sponsored Retirement Plan Redeem by Telephone: You may sell shares held at BlackRock by telephone request. Call (800) 537-4942 for details. The Fund, its administrators and the Distributor will employ reasonable procedures to confirm that instructions communicated by telephone are genuine. The Fund and its service providers will not be liable for any loss, liability, cost or expense for acting upon telephone instructions that are reasonably believed to be genuine in accordance with such procedures. The Fund may refuse a telephone redemption request if it believes it is advisable to do so. During periods of substantial economic or market change, telephone redemptions may be difficult to complete. Please find below alternative redemption methods. Redeem by Internet: You may redeem in your account, by logging onto the BlackRock website at www.blackrock.com. Proceeds from Internet redemptions will be sent via wire to the bank account of record. Redeem in Writing: Redemption requests may be sent in proper form to BlackRock, P.O. Box 9819, Providence, Rhode Island 02940-8019 or for overnight delivery, 4400 Computer Drive, Westborough, Massachusetts 01588. Under certain circumstances, a medallion signature guarantee will be required. Payment of Redemption Proceeds Redemption proceeds may be paid by check or, if the Fund has verified banking information on file, by wire transfer. Payment by Check: BlackRock will normally mail redemption proceeds within seven days following receipt of a properly completed request. Shares can be redeemed by telephone and the proceeds sent by check to the shareholder at the address on record. Shareholders will pay $15 for redemption proceeds sent by check via overnight mail. You are responsible for any additional charges imposed by your bank for this service.

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	Your Choices	Important Information for You to Know
Full or Partial Redemption of Shares (continued)	Selling shares held directly with BlackRock (continued)	The Fund reserves the right to reinvest any dividend or distribution amounts (e.g., income dividends or capital gains) which you have elected to receive by check should your check be returned as undeliverable or remain uncashed for more than 6 months. No interest will accrue on amounts represented by uncashed checks. Your check will be reinvested in your account at the net asset value next calculated, on the day of the investment. When reinvested, those amounts are subject to the risk of loss like any fund investment. If you elect to receive distributions in cash and a check remains undeliverable or uncashed for more than 6 months, your cash election may also be changed automatically to reinvest and your future dividend and capital gains distributions will be reinvested in the Fund at the net asset value as of the date of payment of the distribution. Payment by Wire Transfer: Payment for redeemed shares for which a redemption order is received before 4:00 p.m. (Eastern time) on a business day is normally made in Federal funds wired to the redeeming shareholder on the next business day, provided that the Fund’s custodian is also open for business. Payment for redemption orders received after 4:00 p.m. (Eastern time) or on a day when the Fund’s custodian is closed is normally wired in Federal funds on the next business day following redemption on which the Fund’s custodian is open for business. The Fund reserves the right to wire redemption proceeds within seven days after receiving a redemption order if, in the judgment of the Fund, an earlier payment could adversely affect the Fund. Shares can be redeemed by Federal wire transfer to a single previously designated bank account. No charge for wiring redemption payments with respect to Class K Shares is imposed by the Fund. You are responsible for any additional charges imposed by your bank for wire transfers. The Fund is not responsible for the efficiency of the Federal wire system or the shareholder’s firm or bank. To change the name of the single, designated bank account to receive wire redemption proceeds, it is necessary to send a written request to the Fund at the address on the back cover of this prospectus. *** If you make a redemption request before the Fund has collected payment for the purchase of shares, the Fund may delay mailing your proceeds. This delay will usually not exceed ten days.

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How to Transfer Your Account

	Your Choices	Important Information for You to Know
Transfer Shares to Another Financial Intermediary	Transfer to a participating Financial Intermediary	You may transfer your Class K Shares of the Fund only to another Financial Intermediary that has entered into an agreement with the Distributor. Certain shareholder services may not be available for the transferred shares. All future trading of these assets must be coordinated by the receiving firm. Please contact your Financial Intermediary to accomplish the transfer of shares.
	Transfer to a non-participating Financial Intermediary	You must either: •    Transfer your Class K Shares to an account with the Fund; or •    Sell your Class K Shares. Please contact your Financial Intermediary to accomplish the transfer of shares.

Additional Purchase and Redemption Information Applicable to the Fund if You Are Not Purchasing Shares Through an Employer-Sponsored Retirement Plan

If you are not purchasing shares through an Employer-Sponsored Retirement Plan, the Fund may authorize one or more banks, savings and loan associations and other financial institutions (each a “Service Organization”) to accept purchase and redemption orders on its behalf. Such Service Organizations may be authorized to designate other intermediaries to accept purchase and redemption orders on the Fund’s behalf. If you purchase or redeem shares through a Service Organization or its designee, that entity may have its own deadlines for the receipt of the purchase or redemption order that may be earlier than those stated in the prospectus. The Fund will be deemed to have received a purchase or redemption order when a Service Organization or, if applicable, that Service Organization’s authorized designee, accepts the order. These orders will be priced at the Fund’s net asset value per share next calculated after they are so accepted.

Shareholders should retain this Supplement for future reference.

PRO-CAPNYMBL-0516SUP

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