EXHIBIT 21.1 SUBSIDIARIES OF ORION POWER HOLDINGS, INC. Orion Power Capital, LLC Orion Power MidWest LP, LLC Orion Power MidWest, L.P. Twelvepole Creek, LLC Orion Power New York LP, LLC. Orion Power New York, L.P. Astoria Generating Company, L.P. Erie Boulevard Hydropower, L.P. Orion Power Development Company, Inc. Liberty Member, LLC Liberty MidAtlantic, LLC Liberty Electric PA, LLC Liberty Electric Power, LLC Orion Power MidWest GP, Inc. Orion Power New York GP, Inc. Carr Street Generating Station, L.P. Orion Power New York GP II, Inc. Orion Power Operating Services, Inc. Orion Power Marketing and Supply, Inc. Orion Power Operating Services Midwest, Inc. Orion Power Operating Services Astoria, inc. Orion Power Operating Services Coldwater, Inc. Orion Power Operating Services Carr Street, Inc. OPOS MidAtlantic, Inc. OPD Group, Inc. Beaver River, LLC Grane Creek, LLC Free State Electric, LLC Orion Power Atlantic, Inc. Orion Power Atlantic, LLC Orion Power Atlantic, Ltd. Midwest Ash Disposal, Inc. MidAtlantic Library, LLC Eddystone Power, LLC