That must have been AM 89 WLS.... That was our go to station before we discovered FM....
I was talking to Mr. Norm at a car show and he was telling me that he used to advertise on WLS at night because they broadcasted from the Sears Tower... They were not allowed to run full power during the day (regulations), but at night (after midnight I believe) they were allowed to run their broadcasting towers on full blast and his advertisements could be heard from the east coast to the west coast on clear nights... He intentionally did that to get the maximum audience for his advertising...
Smart man... Advertise on a radio station that broadcasted from the tallest building in the world when the power was turned on full blast....