On July 1, 1954, KECI debuted as KGVO-TV, owned by Montana broadcasting pioneer Arthur Mosby, along with KGVO radio (1290 AM). Because of its radio sister's lengthy association with CBS radio, the station was initially a major CBS affiliate, although it also ran programming from ABC and DuMont; it would lose DuMont when the network shut down in 1956. On December 1, 1956, the station's studios were relocated from its transmitter position to its radio sister's facilities on West Main Street in downtown Missoula, and its call letters were changed to KMSO-TV. KMSO had a secondary connection with NBC by 1957. Mosby sold KGVO radio to Dale Moore in 1959, but kept KMSO until 1964, when Moore purchased channel 13. When he took over, he changed the station's call letters back to KGVO-TV.