From the southwest suburbs of Chicago ...
In the beginning, there was WOAI San Antonio, which enjoys the distinction of having been the last clear-channel station to have its frequency all to itself – according to the White's Radio Log I started with in the early 1970s.
In these parts, what is now WRTO started as WMXA, has also been WOPA, WLXX and WVIV along the way, and has a transmitter in Chicago's West Pullman district after previously been located nearby at I-94 and 103rd Street. The new location also meant a signal boost day (from 5 kW to 20 kW) and night (from 1 kW to 4.5 kW). Day and night patterns are different.
I'm near enough so WRTO is hard to null, but if I really work at it, hints of WOAI come through.
Once upon a time in the early 1980s, a pirate showed up here, identifying as KDF677 Addison, Ill. and boasting 100-watt power and as "WLS-owned." Heard it one night and never again.