Jack FM Denver was the first Jack radio station in the United States. 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. Each Jack station is a little different, and KJAC's attention to the style of Colorado gave the station a unique and local feel.
On September 1, 2008, NRC Broadcasting converted KCUV into a rebroadcast of the current Jack FM feed, utilizing the 102.3 FM frequency to serve the broader Denver metropolitan area, while retaining the current 105.5 FM frequency that serves Northern Colorado. Jingles broadcast over the air often interchanged 102.3 FM and 105.5 FM, depending on whether the focus was on Denver, or the station in general. On July 15, 2010, it was announced that KJAC would stick with the current format while sister station KDSP flipped to sports on July 19, 2010. In 2011 105.5 Jack FM dropped the local version and started using the Dial Global StorQ version that smaller market Jacks use.
On September 7, 2012, KJAC started stunting with sports clips leading to a flip to ESPN Radio.