In 1978, 103.9 signed on as KBON with a beautiful music format to represent the rapidly growing Riverside-San Bernardino radio market's full potential. The signal was strong enough to reach the Morongo Basin and the Victor Valley areas.
In 1987, KBON again changed formats to traditional oldies.
On September 1, 1992, KBON became KCKC-FM making 103.9 a full AM/FM simulcast with KCKC-AM 1350 AM. KCKC-AM had been broadcasting in San Bernardino for 25 years (from 1966 to 1992) with a country music format.
On October 31, 1993, KCKC-FM became KABE as it changed to a simulcast of another 103.9 FM KACE which broadcast to the nearby Los Angeles area. Covering most of Los Angeles and the Inland Empire, the simulcast briefly experimented with a hip hop/R&B format as V103.9.
On October 2, 1994, KABE became KAEV following the political and social backlash against hip-hop music. The owners of the station announced an outright prohibition of several derogatory words on air and shifted to a "Positive Urban" format. However, this lowered ratings significantly and on January 1, 1995 KAEV became KCXX and ended its simulcast with KACE, with the first song played being "Closer" by Nine Inch Nails. 2015 was KCXX's 20th Anniversary of operation as an Alternative Rock station.