Transtar>Westwood One>Dial Global. I think there was a Unistar somewhere in there, too.
I remember when Format 41 went on the air in the late 80s in Sioux City, replacing a beautiful music format. The other FMs were CHR, AOR, and religion. The AMs were talk, country, and oldies. Format 41 took off, number one 25-54 despite being all satellite, nothing local except a few news updates. Their dominance lasted for two or three years until a new country FM went on the air, live 24/7. The Format 41 station took a major dive, the owner decided what was needed was Imus In The Morning. Of course, this was incompatible. Imus stayed, several other satellite music formats were tried, none worked. Under different owners, Imus was dropped, it went Classic Rock and is doing very well.
Format 41 (I think it was called Soft AC at this point) later returned to Sioux City on a new FM, and did OK. Later CC bought the station, did their own lite AC for awhile, and it's now CHR. Right now the only AC in the market is CC's Hot AC. I think there's a pretty big hole for a lite AC again.