Exhibit 21 BLACK HILLS CORPORATION SIGNIFICANT DIRECT AND INDIRECT SUBSIDIARIES Black Hills Power, Inc., South Dakota corporation Black Hills Energy Ventures, Inc., a South Dakota corporation Black Hills Energy Capital, Inc., a Delaware corporation Wyodak Resources Development Corp., a Delaware corporation Adirondack Hydro Development Corporation, a Delaware corporation Black Hills Capital Group, Inc., a South Dakota Corporation Black Hills Coal Network, Inc., a South Dakota corporation Black Hills Colorado, LLC, a Delaware corporation Black Hills Energy Resources, Inc., a South Dakota corporation Black Hills Exploration and Production, Inc., a Wyoming corporation Black Hills FiberCom, LLC, a South Dakota corporation Black Hills Fiber Systems, Inc., a South Dakota corporation Black Hills Generation, Inc., a Wyoming corporation Daksoft, Inc., a South Dakota corporation Enserco Energy, Inc., a South Dakota corporation Hudson Falls, LLC, a New York corporation Landrica Development Company, a South Dakota corporation South Glens Falls, LLC, a New York corporation