EXHIBIT 21 SUBSIDIARIES OF THE REGISTRANT WPS RESOURCES CORPORATION 1) WPS RESOURCES CORPORATION * a) Wisconsin Public Service Corporation i) WPS Leasing, Inc. b) Upper Peninsula Power Company c) WPS Visions, Inc. d) Upper Peninsula Building Development Company e) Penvest, Inc. f) WPSR Capital Trust I g) WPS Nuclear Corporation i) Nuclear Management Company, LLC (25% ownership) h) WPS Resources Capital Corporation i) WPS Energy Services, Inc. (1) WPS-ESI Gas Storage, LLC (75% ownership) ii) WPS Power Development, Inc. (1) PDI Stoneman, Inc. (a) Mid-American Power, LLC (66-2/3% ownership) (2) PDI Operations, Inc. (3) Mid-American Power Ventures, LLC (75% ownership) (4) Neulite Industries of Wisconsin, LLC (50% ownership) (5) PDI Canada, Inc. (6) PDI New England, Inc. (7) Sunbury Holdings, LLC (a) Sunbury Generation, LLC (b) Penfield Collieries, LLC (8) Renewable Fibers International, LLC (33-1/3% ownership) (9) Wisconsin Woodgas LLC (10) Wisconsin Energy Operations LLC (49% ownership) (11) ECO Coal Pelletization #12, LLC (66-2/3% ownership) i) Brown County C-LEC, LLC (40% ownership) * WPS Resources Corporation is the parent holding company. All affiliated companies listed are 100% owned except as noted otherwise. All affiliated companies are currently active, with the exception of Mid-American Power Ventures, LLC and Neulite Industries of Wisconsin, LLC. E-240