Exhibit 21 BLACK HILLS CORPORATION SUBSIDIARY OF REGISTRANT Wyodak Resources Development Corp., a Delaware corporation. SUBSIDIARIES OF WYODAK RESOURCES DEVELOPMENT CORP. DAKSOFT, Inc. a South Dakota corporation. Landrica Development Company, a South Dakota corporation. Western Production Company, a Wyoming corporation. WYGEN, Inc. a Wyoming corporation. Enserco Energy, Inc. a South Dakota corporation. (50 percent owned by Wyodak Resources)