The station previously aired an adult hits music format branded as "Jack FM".

Denver's Jack employed a comedic irreverence in its presentation, and a style of music endemic to the varied tastes of Colorado's front-range listeners.

On September 7, 2012, KJAC started stunting with classic country as "Bob FM", which led to a flip to ESPN Radio.

[2] On December 7, 2015, Front Range Sports Networks sold KJAC to Community Radio for Northern Colorado, who converted the station to a non-commercial Adult Album Alternative format on February 29, 2016, allowing primary station KUNC/Fort Collins, Colorado to focus on News/Talk programming.

After KJAC ended its programming on January 3, 2016, ESPN Radio returned to former Denver affiliate KEPN in a full-time status with sister KKFN adding overnight programming (and dropping Fox Sports Radio from the schedule) starting January 4.