Owned by Audacy, Inc. and branded as "US✶99", it is based at Two Prudential Plaza in the Loop, and transmits from atop the John Hancock Center with an HD Radio signal.

[3][9] In May 1940, the Federal Communications Commission (FCC) announced the establishment, effective January 1, 1941, of an FM radio band operating on 40 channels spanning 42–50 MHz.

[28][29][23] In 1966, the station began to sell advertising time, though commercials were limited to five minutes per hour and the ads had to be compatible with WEFM's classical music format.

[4] In the early 1970s Zenith agreed to sell WEFM to General Cinema Corporation, which intended to change the station's call letters to WICV (pseudo-Roman numerals for 99.5) and institute a rock format.

[24] General Cinema converted the station to a top 40 format with program director Brian White and afternoon drive personality Don Cox, but decided not to change the call sign.

[25][30][31] The station was branded "We-FM" and initially broadcast from the studios used by the Zenith classical music format at 120 West Madison street in the Chicago loop.

[38] Lee Logan was hired as program director from KFMK in Houston, remaining with the station until 1987, when he departed for KLAC in Los Angeles.

[52][53] In 1967, WEFM won the National Federation of Music Clubs' "Special 4-Star Award" for "outstanding programming devoted to American composers".

[55][56][57] In 2005, WUSN host Lisa Dent won the Country Music Association's Major Market Personality of the Year award.

[61] On July 7, 2003, country music radio personality Cliff Dumas sued Infinity Broadcasting Corporation and WUSN in United States District Court, seeking monetary damages.