UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) x Quarterly Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the quarterly period ended March 31, 2019 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 1-3548 ALLETE, Inc. (Exact name of registrant as specified in its charter) Minnesota 41-0418150 (State ...