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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , DC 20549 Form 10 - K > ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 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 001-31303 BLACK HILLS CORPORATION Incorporated in South Dakota IRS Identification Number 46-0458824 7001 Mount Rushmore Road Rapid City , South Dakota 57702 Registrant's telephone number ( 605 ) 721-1700 Title of each class Common stock of $ 1.00 par value Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol BKH Name of each exchange on which registered New York Stock Exchange Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes ☑No ☐ Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes ☐ No ☑ 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 > No ☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted 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 such files ) . Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , smaller reporting company , or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer Non - accelerated filer ☑ Accelerated filer ☐ Smaller reporting company Emerging growth company ☐ ☐ ☐ If an emerging growth company , indicate by check mark if the Registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . ☐ Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C.7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . ☑ Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes ☐ No ☑ The aggregate market value of the voting common equity held by non - affiliates of the registrant on the last business day of the registrant's most recently completed second fiscal quarter , June 30 , 2020 , was $ 3,528,768,075 Indicate the number of shares outstanding of each of the registrant's classes of common stock , as of the latest practicable date . Class Common stock , $ 1.00 par value Outstanding at January 31 , 2021 62,794,490 shares Documents Incorporated by Reference Portions of the registrant's Definitive Proxy Statement being prepared for the solicitation of proxies in connection with the 2021 Annual Meeting of Stockholders to be held on April 27 , 2021 , are incorporated by reference in Part III of this Form 10 - K .