I found some info on early WGN programs, I've reproduced it here, it's from the Tribune Archives. I remember listening in the late 40's and early 50's and WGN had a lot of local produced radio. Note the arrival of FM in 1941. Note below that over 7000 people attend WGN programs each week. In addition WGN was the Mutual Network station in Chicago. WGN being clear channel did a lot of farm reporting in the morning as well.
Here's the stuff from the Trib:
Chicago Daily Tribune (1940 - 1950) - Chicago, Ill. Date: Oct 21, 1945 Start Page: s8 Section: S Document Types: article Text Word Count: 196
A new half hour transcribed radio program, "Youth Looks Up," will make its debut on W-G-N. The program will be heard at 8 a. m.
Citizens of Tomorrow radio show dedicated to the high school set, will return to W-G-N tomorrow at 9:30 a.m.
So you want to see a radio show broadcast. Well, you may have to wait a few days, but chances are you'll get the tickets. There are many possibilities in Chicago. An average of about 7,000 persons see W-G-N broadcasts every week.
9/21/41 A new thrill awaits numerous Chicagoland listeners today with the normal opening by W-G-N of a sister station, W59C. This new frequency modulation [FM]
Preparing for the post-war expansion in the field of high fidelity, static free frequency modulation radio WGNB, sister station of W-G-N, today will introduce a new program policy with emphasis on the best in music and "live" broadcasts, under the direction of Marion...Authority to construct a frequency modulation [F-M] radio station immediately was granted to W-G-N, Inc., yesterday by the Federal Communications commission in Washington, D. C. The FCC order authorized W-G-N, Inc., to construct station W59C, to operate.