The station was founded in 1977 by broadcast engineer Paul Posen under his company, Classic Broadcasting. The original call sign was KCMS, changing to the current KEZN call sign in 1983. Studios were originally based in Indio and broadcast a classical music format, hence the company name.
By 1987, the studios were moved to a new facility in Palm Desert where they remain to this day. In the early 1990s, the station began to shift toward a very mellow format with the broadcast of "Format 41," the soft rock music service of Westwood One. In 1994, KEZN became the only Soft Rock AC station in the Palm Springs market with the changeover of KPLM to a contemporary country music format. Legendary Los Angeles broadcaster Russ O'Hara teamed with local personality Kayla Stone for the "Russ and Kayla" morning drive slot; another local favorite, Debra Kaye Ahlers occupied the mid day shift; Orange County favorite Dale Berg, the PD handled Afternoon Drive. Morning drive has been occupied for several years by former Nashville Network announcer Dan McGrath while former KCLB personality John O (John Ostrum) occupies the afternoon drive. Gary Bell came to the station in 1996 from KCBS-FM, Los Angeles and has been there since. Ryan Yamanaka also served as an on-air personality from 2000 - 2001 working the 12am-6am shift. He was also the last of few who drove KEZN's "Mr. Frosty". The early personalities helped propel KEZN to the highest rated adult station in the market. By the fall of 1997, KEZN showed a 23 share with women 25 to 54 in middays according to Arbitron.
Posen sold his interest in the station in 1997 to a firm that would later be absorbed by CBS. KEZN was operated under the CBS Radio banner for several years afterward, switching later to Viacom'sInfinity Broadcasting banner after absorbing CBS. The station has since reverted to the CBS Radio banner since the corporate dismantling of Infinity Broadcasting by its parent company.
On December 26th, 2014, after airing its annual Christmas music format since November, KEZN rebranded as "103.1 Sunny FM", with no other changes.