On May 11, 2009, Black Hills Corporation (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") with Credit Suisse Securities (USA) LLC and RBS Securities Inc., acting for themselves and as representatives of the several underwriters named in Schedule A to the Underwriting Agreement, in connection with an underwritten public offering (the "Offering") of $250 million aggregate principal amount of 9% notes due 2014 (the "Notes"). The Notes have been registered under the Securities Act of 1933, as amended, pursuant to the Company's existing shelf registration statement (File No. 333-150669) (the "Registration Statement"). The closing of the Offering is expected to occur on May 14, 2009, subject to satisfaction of customary closing conditions.

The Company intends to use the net proceeds of the Offering to repay a portion of the borrowings under its $383 million acquisition credit facility with The Royal Bank of Scotland Group, as successor administrative agent, and certain other lenders. The acquisition credit facility provided funding for a portion of the purchase price for the Company's acquisition of Aquila, Inc.'s regulated electric utility in Colorado and its regulated gas utilities in Colorado, Kansas, Nebraska and Iowa, and expires on December 29, 2009.

A copy of the Underwriting Agreement is attached as Exhibit 1 hereto and is incorporated by reference into this Item 1.01 as though fully set forth herein.

This Current Report on Form 8-K shall not constitute an offer to sell or a solicitation of an offer to buy the securities described herein, nor shall there be any sale of these securities in any state or jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. The Offering is being made only by means of a prospectus and related prospectus supplement.

The Company is offering and selling the Notes under the Registration Statement and accompanying prospectus and prospectus supplement, which Registration Statement relates to the offer and sale on a delayed basis from time to time of an indeterminate amount of the Company's securities. This Current Report on Form 8-K is being filed in connection with the offer and sale of the Notes as described herein and to file with the Securities and Exchange Commission in connection with the Registration Statement the documents and instruments attached hereto as exhibits. A copy of the Press Release announcing the pricing of the Notes is also attached as Exhibit 99 hereto.

(d) Exhibits.

The Registrant files the following exhibits as part of this report:

Exhibit 1   Underwriting Agreement dated May 11, 2009, among the Company and
            Credit Suisse Securities (USA) LLC and RBS Securities Inc., acting
            for themselves and as representatives of the several underwriters.

Exhibit 4   Form of Second Supplemental Indenture dated as of May 14, 2009,
            between the Company and Wells Fargo Bank, National Association, as
            trustee.

Exhibit 5.1 Opinion of Steven J. Helmers regarding the legality and enforceability of the Notes.

Exhibit 5.2 Opinion of Conner & Winters, LLP.

Exhibit 23.1 Consent of Steven J. Helmers (included in Exhibit 5.1).

Exhibit 23.2 Consent of Conner & Winters, LLP (included in Exhibit 5.2).

Exhibit 25   Form T-1 Statement of Eligibility of Wells Fargo Bank, National
             Association.

Exhibit 99   Press Release, dated May 11, 2009.