The station went on the air as KLSZ on September 12, 1972. On 1985-09-25, the station changed its call sign to KLSC. On 1987-04-01 to KYBG and finally on 1996-06-07 to the current KMXA. In the late 1980s and into the 1990s, the station, under the call sign KYBG, was the first all-sports radio station west of the Mississippi River. Irv Brown was an early host on the station as well.
As of June 3, 2015 the station now broadcasts the Entravision "Super Estrella" Spanish CHR format.
In the 1980s, the station's callsign was KLDR (now used by a station in Medford, Oregon). The station's format was current and oldies top 40, with the playlist totally determined by listeners' requests. It promoted itself as "Colorado's all-request station." KLDR also carried broadcasts of Colorado State Rams football.