KECI hit the airwaves on July 1, 1954 as KGVO-TV, owned by Montana broadcasting pioneer Arthur Mosby along with KGVO radio (1290 AM). Originally, the station was a primary CBS affiliate, owing to its radio sister's long affiliation with CBS radio, but also carried programming from ABC and DuMont; it would lose DuMont when the network shut down in 1956. On December 1, 1956, the station's studios moved from its transmitter location to its radio sister's studios on West Main Street in downtown Missoula, and concurrently changed its call letters to KMSO-TV. By 1957, KMSO had added a secondary affiliation with NBC. Mosby sold KGVO radio to Dale Moore in 1959, but held on to KMSO until 1964, when Moore bought channel 13 as well; upon taking over, he changed its call letters back to KGVO-TV.