UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q/A

Amendment No. 1

(mark one)
x	QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
For the quarterly period ended September 30, 2010
OR
¨	TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from          to          

Commission File Number: 1-10499

[Missing Graphic Reference]

NORTHWESTERN CORPORATION

Delaware	46-0172280
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)
3010 W. 69th Street, Sioux Falls, South Dakota	57108
(Address of principal executive offices)	(Zip Code)
Registrant’s telephone number, including area code: 605-978-2900

	Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or
15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No o
Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). Yes x No o
	Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non- accelerated
filer or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.
Large Accelerated Filer x        Accelerated Filer o        Non-accelerated Filer o        Smaller Reporting Company o
	Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange
Act). Yes o  No x
	Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest
practicable date:

Common Stock, Par Value $0.01

36,205,295 shares outstanding at October 22, 2010

EXPLANATORY NOTE

NorthWestern Corporation (the Company) is filing this Amendment No. 1 (this “Form 10-Q/A”) to its Quarterly Report on Form 10-Q for the quarter ended September 30, 2010, filed with the Securities and Exchange Commission on October 28, 2010 (the “Form 10-Q”), for the sole purpose of furnishing the Interactive Data File as Exhibit 101. The Interactive Data File was inadvertently omitted from the Form 10-Q due to technical difficulties associated with the Company’s use of its EDGAR filing software.

No other changes have been made to the Form 10-Q and this Form 10-Q/A does not modify or update any related disclosures made in the Form 10-Q.

PART II – OTHER INFORMATION

ITEM 6.                      EXHIBITS

See Index to Exhibits beginning on page 3.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

		Northwestern Corporation
Date: October 28, 2010	By:	/s/ KENDALL G. KLIEWER
		Kendall G. Kliewer
		Vice President and Controller
		Duly Authorized Officer and Principal Accounting Officer

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EXHIBIT INDEX

Exhibit Number	Description
**31.1	Certification of chief executive officer.
**31.2	Certification of chief financial officer.
**32.1	Certification of chief executive officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
**32.2	Certification of chief financial officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
*101.INS	XBRL Instance Document
*101.SCH	XBRL Taxonomy Extension Schema Document
*101.CAL	XBRL Taxonomy Extension Calculation Linkbase Document
*101.DEF	XBRL Taxonomy Extension Definition Linkbase Document
*101.LAB	XBRL Taxonomy Label Linkbase Document
*101.PRE	XBRL Taxonomy Extension Presentation Linkbase Document

** Previously filed on October 28, 2010, as part of the original filing of the Form 10-Q as of September 30, 2010 (File No. 1-10499).

* Furnished with this report. In accordance with Rule 406T of Regulation S-T, the information in these exhibits shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to liability under that section, and shall not be incorporated by reference into any registration statement or other document filed under the Securities Act of 1933, as amended, except as expressly set forth by specific reference in such filing.

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