The station's studio is in the Old Union building on the campus of Illinois State University. Its callsign comes from the motto of Illinois State University: "Gladly we Learn and Teach", originally "and gladly wold he lerne and gladly teche", from line 309 of The Canterbury Tales.
WGLT signed on the air on February 6, 1966, with only 10 watts of power and a studio in Cook Hall. It was originally student-run and heard only in the dorms. WGLT increased power to 2300 watts and became a full-powered NPR station in July 1976, and increased power to 25,000 watts effective radiated power and adopted jazz as its daytime format in August 1992. The Blues Radio channel started on the Internet in March 2006, and the HD Radio broadcasts began in October 2008 with the main WGLT program on HD1, Blues Radio on HD2, and a News & Ideas channel on HD3.
On August 5, 2013, WGLT dropped Jazz programming from its daytime schedule to concentrate on News/Talk full-time due to declining ratings, but continues to air Jazz on its internet stream. In addition, its HD subchannels ceased operations due to a lack of listenership and interest in the specialty formats.