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) Black Hills Capital Group, Inc. a South Dakota corporation Black Hills Energy Resources, Inc. a South Dakota corporation VariFuel, Inc. a South Dakota corporation