Following the establishment of the Federal Radio Commission (FRC), stations were initially issued a series of temporary authorizations starting on May 3, 1927,[7] and later that year, WCLS's frequency was changed to 1390 kHz.

[2] In addition, stations were informed that if they wanted to continue operating, they needed to file a formal license application by January 15, 1928, as the first step in determining whether they met the new "public interest, convenience, or necessity" standard.

[8] On May 25, 1928, the FRC issued General Order 32, which notified 164 stations, including WCLS, that "From an examination of your application for future license it does not find that public interest, convenience, or necessity would be served by granting it.

It became a full-time news/talk station by 2001. Notable radio personalities that have worked at WJOL include Frank O'Leary, Don Ladas, Kevin Kollins, Bill Drilling, Art Hellyer, Bob Zak, Don Beno, Tony Ray, Ralph Sherman Sr., Jerry Halasz, Max Carey, Ron Gleason, Joe Tippett, John Dempsey, Bob Wheeler and Ruth Stevens, who did a radio show from her record shop and was the first black woman on the station.

[citation needed] While working at the station during its WCLS era, sportscaster Harry Caray adopted his on-air professional name which he would use for the rest of his career.