Due to its location near the bottom of the AM dial, as well as its transmitter power, directional antenna and central Illinois's flat land (with high ground conductivity), its daytime footprint is almost as large as that of a full-power FM station.

In mid-1920 the University of Illinois at Urbana was issued an Experimental radio station license with the call sign 9XJ.

[5] Although primarily used for technical training and experimental purposes, by 1921 9XJ was also being used to broadcast athletic scores,[6][7] and in early 1922 plans were announced to add musical presentations.

In early March it was announced that preparations were being made to apply for a Limited Commercial license that authorized broadcasting, in addition to point-to-point communication with other universities.

[14] This financed the purchase of a 1,000 watt transmitter, plus construction at 400 South Wright Street of a new studio building and "flat-top" antenna structure.

[15] On November 11, 1928, under the provisions of the Federal Radio Commission's General Order 40, the station's frequency was changed to 890 kHz, on a timeshare basis with KUSD in Vermillion, South Dakota and KFNF in Shenandoah, Iowa.

In late 1942 the university began operating an FM station, originally WIUC (now WILL-FM), which allowed for the addition of regular nighttime programming after WILL was required to sign-off at sunset.