Northern States Power and Wisconsin Energy Corporation had planned to merge into a new outfit that was to be called Primergy - but in 1997, the merger fell through because of the time it was taking to gain the required approvals from state and federal agencies. After the failed Primergy merger, NSP (both the Minnesota and Wisconsin companies) merged with New Century Energies to form Xcel Energy. In 2005, Xcel sold Cheyenne Light, Fuel and Power to Black Hills Corporation. Cheyenne Light, Fuel and Power had been a subsidiary of PSCo since the 1920s, and had become an operating company of NCE after the merger with SPS.