WENR became active in late 1924 and early 1925, the creation of E. N. Rauland, whose company manufactured the All-American brand of radios. Rauland started with 10 watts on 1030 kHz in 1924; on March 19, 1925, he received his license for WENR at 100 watts. By late 1925 WENR was using a 1000 watt transmitter designed by Rauland himself. The station quickly entered into a time-sharing agreement with WBCN, owned at that time by the Chicago Southtown newspaper. The two stations changed frequencies to 1040 kHZ a year later.
By 1927, Chicago investor Samuel Insull had taken serious interest in both stations. A founding partner of KYW, he sold his interest in it and had started Great Lakes Broadcasting. Insull purchased both stations, paying $1 million for WENR alone. Under Insull's management, the two stations once more changed frequencies, this time to 870 kHz, when the combined stations became the first Chicago radio station operating under 50,000 watts of power from a new transmitter in Downers Grove, Illinois in 1929. Insull's Great Lakes Broadcasting holdings also included a mechanical television station, W9XR, which went on the air after the Downers Grove transmitter was installed. Insull moved his stations first into Chicago's Strauss Building, and then to his own Civic Opera House. The investor's fortune began dwindling by 1931; Insull then sold the licenses of both stations to National Broadcasting Company. By early 1933, WBCN's call letters had left the airwaves and the frequency was occupied by WENR, which became part of NBC's Blue Network, and by WLS. NBC shut down W9XR by 1933, just as it had done with WX9AP, which it acquired in its purchase of radio station WMAQ.
Changes were made regarding AM frequencies in 1941 as a result of the North American Radio Broadcasting Agreement; this moved WENR and WLS from 870 kHz to 890 kHz. In August 1943, NBC was ordered to divest itself of the Blue Network and its stations; WENR and Blue were sold to Edward J. Noble. In 1945 the Blue Network would be renamed as the American Broadcasting Company. The 1931 sale of the station to NBC moved WENR from the Civic Opera House to the Merchandise Mart, NBC's Chicago headquarters. The station continued on at the Mart until 1952 by becoming NBC's tenant, moving back to the Civic Opera House in that year. Paul Harvey's Chicago broadcasting career began at WENR.
WENR and WLS used the same frequencies in a time-sharing arrangement until 1954, when ABC (then known as American Broadcasting-Paramount Theatres) bought a 50 percent interest in WLS and combined the stations. In November 1959 ABC announced its purchase of the Prairie Farmer and its half of WLS, giving ABC full ownership of the station.