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( Mark One ) Annual Report Pursuant to Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 For the year ended December 31 , 2020 United States Securities and Exchange Commission Washington , D.C. 20549 Form 10 - K Transition Report Pursuant to Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 For the transition period from to Minnesota ( State or other jurisdiction of incorporation or organization ) Title of each class Common Stock , without par value Commission File Number 1-3548 ALLETE , Inc. ( Exact name of registrant as specified in its charter ) Emerging Growth Company 30 West Superior Street , Duluth , Minnesota 55802-2093 ( Address of principal executive offices , including zip code ) ( 218 ) 279-5000 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ALE Securities registered pursuant to Section 12 ( g ) of the Act : None Accelerated Filer 0 Smaller Reporting Company ☐ 41-0418150 ( I.R.S. Employer Identification No. ) Indicate by check mark if the registrant is a well - known seasoned issuer , as defined Rule 405 of the Securities Act . Yes > 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 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 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 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 , a 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 Name of each exchange on which registered New York Stock Exchange No No X 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 X The aggregate market value of voting stock held by nonaffiliates on June 30 , 2020 , was $ 2,825,208,722 . As of February 1 , 2021 , there were 52,116,629 shares of ALLETE Common Stock , without par value , outstanding . Documents Incorporated By Reference Portions of the Proxy Statement for the 2021 Annual Meeting of Shareholders are incorporated by reference in Part III .