| x      | ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934     |
|--------|------------------------------------------------------------------------------------------|
|   |                                                                                     |
|   | For the fiscal year ended December 31, 2009                                              |
|   |                                                                                     |
| o      | 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 1-7978                                                            |

| Incorporated in South Dakota                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |   | IRS Identification Number 46-0111677 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|--------------------------------------|
| 625 Ninth Street, Rapid City, South Dakota  57701                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |   |                                 |
| Registrant's telephone number, including area code: (605) 721-1700                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |   |                                 |
| Securities registered pursuant to Section 12(b) of the Act:                                                                                                None |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |   |                                 |
| Securities registered pursuant to Section 12(g) of the Act:                                                                                                None |

| Class                         | Outstanding at February 26, 2010 |
|-------------------------------|----------------------------------|
| Common stock, $1.00 par value | 23,416,396 shares                |

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| ITEM 15. | EXHIBITS, FINANCIAL STATEMENT SCHEDULES |
|----------|-----------------------------------------|

| (a)    | 1.     | Financial Statements                                                                                                                                                                                                           |
|--------|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |   |                                                                                                                                                                                                                           |
|   |   | Financial statements required by Item 15 are listed in the index included in Item 8 of Part II.                                                                                                                                |
|   |   |                                                                                                                                                                                                                           |
|   | 2.     | Schedules                                                                                                                                                                                                                      |
|   |   |                                                                                                                                                                                                                           |
|   |   | Valuation and Qualifying Accounts for the years ended December 31, 2009, 2008 and 2007.                                                                                                                                        |
|   |   |                                                                                                                                                                                                                           |
|   |   | All other schedules have been omitted because of the absence of the conditions under which they are required or because the required information is included elsewhere in the financial statements included in this Form 10-K. |

| BLACK HILLS POWER, INC.VALUATION AND QUALIFYING ACCOUNTSYEARS ENDED DECEMBER 31, 2009, 2008 AND 2007 |
|------------------------------------------------------------------------------------------------------|
|                                                                                                 |
| Additions                                                                                            |
|                                                                                                 |
| Description                                                                                          | Balance at beginning of year | Charged to costs and expenses | Deductions | Balance at end of year |
|                                                                                                 | (in thousands) |
| Allowance for doubtful accounts:                                                                     |   |   |   |   |   |   |   |   |
| 2009                                                                                                 | $ | 370 | $ | 316 | $ | (427) | $ | 259 |
| 2008                                                                                                 | $ | 388 | $ | 637 | $ | (655) | $ | 370 |
| 2007                                                                                                 | $ | 250 | $ | 320 | $ | (182) | $ | 388 |

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| 3. | Exhibits |
|----|----------|

| Exhibit Number |  Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 3.1*           | Restated Articles of Incorporation of the Registrant (filed as an exhibit to the Registrant's Form 8-K dated June 7, 1994 (No. 1-7978)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 3.2*           | Articles of Amendment to the Articles of Incorporation of the Registrant, as filed with the Secretary of State of the State of South Dakota on December 22, 2000 (filed as an exhibit to the Registrant's Form 10-K for 2000).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 3.3*           | Bylaws of the Registrant (filed as an exhibit to the Registrant's Registration Statement on Form S-8 dated July 13, 1999).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 4.1*           | Restated and Amended Indenture of Mortgage and Deed of Trust of Black Hills Corporation (now called Black Hills Power, Inc.) dated as of September 1, 1999 (filed as Exhibit 4.19 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).  First Supplemental Indenture, dated as of August 13, 2002, between Black Hills Power, Inc. and The Bank of New York Mellon (as successor to JPMorgan Chase Bank), as Trustee (filed as Exhibit 4.20 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).  Second Supplemental Indenture, dated as of October 27, 2009, between Black Hills Power, Inc. and The Bank of New York Mellon (filed as Exhibit 4.21 to the Registration Statement on Form S-3 (No. 333-150669-01)). |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.1*          | Restated and Amended Coal Supply Agreement for NS II dated February 12, 1993 (filed as Exhibit 10.1 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.2*          | Second Restated and Amended Power Sales Agreement dated September 29, 1997, between PacifiCorp and Black Hills Power, Inc. (filed as Exhibit 10.2 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.3*          | Reserve Capacity Integration Agreement dated May 5, 1987, between Pacific Power & Light Company and Black Hills Power, Inc. (filed as Exhibit 10.3 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 23*            | Independent Auditors' Consent (filed as Exhibit 23 to the Registrant’s 2009 Form 10-K filed March 10, 2010).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 31.1           | Certification of Chief Executive Officer pursuant to Rule 13a-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |

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| 31.2   | Certification of Chief Financial Officer pursuant to Rule 13a-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                        |
|--------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                                                                                                                                                                     |
| 32.1*  | Certification of Chief Executive Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (filed as Exhibit 32.1 to the Registrant’s 2009 Form 10-K filed March 10, 2010). |
|   |                                                                                                                                                                                                                                     |
| 32.2*  | Certification of Chief Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (filed as Exhibit 32.2 to the Registrant’s 2009 Form 10-K filed March 10, 2010). |

|   | __________________________ |
|--------|----------------------------|

|   | * | Previously filed as part of the filing indicated and incorporated by reference herein. |
|--------|---|----------------------------------------------------------------------------------------|

| (b)   | See (a) 3. Exhibits above. |
|-----------------|----------------------------|

| (c)   | See (a) 2. Schedules above. |
|-----------------|-----------------------------|

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|                                                                                      | BLACK HILLS POWER, INC.                                                             |
|-------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------|
|                                                                                      |                                                                                |
|                                                                                      | By                                                                                  | /s/ ANTHONY S. CLEBERG |
|                                                                                      | Anthony S. Cleberg, Executive Vice President  and Chief Financial Officer |
|                                                                                      |                                                                                |
|                                                                                      |                                                                                |
| Dated:           February 14, 2011 |                                                                                |

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| Exhibit Number |  Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 3.1*           | Restated Articles of Incorporation of the Registrant (filed as an exhibit to the Registrant's Form 8-K dated June 7, 1994 (No. 1-7978)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 3.2*           | Articles of Amendment to the Articles of Incorporation of the Registrant, as filed with the Secretary of State of the State of South Dakota on December 22, 2000 (filed as an exhibit to the Registrant's Form 10-K for 2000).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 3.3*           | Bylaws of the Registrant (filed as an exhibit to the Registrant's Registration Statement on Form S-8 dated July 13, 1999).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 4.1*           | Restated and Amended Indenture of Mortgage and Deed of Trust of Black Hills Corporation (now called Black Hills Power, Inc.) dated as of September 1, 1999 (filed as Exhibit 4.19 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).  First Supplemental Indenture, dated as of August 13, 2002, between Black Hills Power, Inc. and The Bank of New York Mellon (as successor to JPMorgan Chase Bank), as Trustee (filed as Exhibit 4.20 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).  Second Supplemental Indenture, dated as of October 27, 2009, between Black Hills Power, Inc. and The Bank of New York Mellon (filed as Exhibit 4.21 to the Registration Statement on Form S-3 (No. 333-150669-01)). |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.1*          | Restated and Amended Coal Supply Agreement for NS II dated February 12, 1993 (filed as Exhibit 10.1 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.2*          | Second Restated and Amended Power Sales Agreement dated September 29, 1997, between PacifiCorp and Black Hills Power, Inc. (filed as Exhibit 10.2 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.3*          | Reserve Capacity Integration Agreement dated May 5, 1987, between Pacific Power & Light Company and Black Hills Power, Inc. (filed as Exhibit 10.3 to the Registrant's Post-Effective Amendment No. 1 to the Registrant's Registration Statement on Form S-3 (No. 333-150669-01)).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 23*            | Independent Auditors' Consent (filed as Exhibit 23 to the Registrant’s 2009 Form 10-K filed March 10, 2010).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 31.1           | Certification of Chief Executive Officer pursuant to Rule 13a-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 31.2           | Certification of Chief Financial Officer pursuant to Rule 13a-14(a) of the Securities Exchange Act of 1934, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 32.1*          | Certification of Chief Executive Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (filed as Exhibit 32.1 to the Registrant’s 2009 Form 10-K filed March 10, 2010).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 32.2*          | Certification of Chief Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (filed as Exhibit 32.2 to the Registrant’s 2009 Form 10-K filed March 10, 2010).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |

|   | __________________________ |
|--------|----------------------------|

|   | * | Previously filed as part of the filing indicated and incorporated by reference herein. |
|--------|---|----------------------------------------------------------------------------------------|

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