As far as ones that stuck around with a format for a long time:

WLIT. It had evolved to Soft AC in the 80s when it was still WLAK. It remained with Soft AC until 100.3 came around with Windy 100 and they tweaked to a more Mainstream AC format. That continued until a decade ago with a short Hot AC run, before going back to AC and Soft AC. Overall WLIT has not been away from AC since the 80s.

WXLC. Until this year, WXLC was CHR from 1980 until 1994 or 1995. Hot AC and Adult CHR variations until the end of last month.

WTMX. They went AC in the late 80s. Hot AC in the 90s. Modern AC in the Mid-late 90s and Adult CHR in the late 2000s. Overall they've been pretty close to Hot AC since the 90s.

US99 has been Country since 1982.

WGCI has been Urban since 1980

WVAZ (Or the 102.7 frequency) has been Urban since 1974

WBBM-AM has been News since 1968


B96 has been a variation of CHR since 1982.


105.1 has been Spanish since 1972

The most format flips would go to 94.7. In late 2000 they went 80s, in Spring 2001 Hot AC, Fall 2001 Alternative, Spring 2003 Active Rock, Fall 2005 Oldies. That was after runs of Classic Rock, Country, Talk, Rhythmic CHR, CHR. The flip to Oldies brought on stability. It tweaked to 70s-80s Classic Hits early last decade and has not changed much since.

100.3's tweaks were always subtle. But it never went too far from AC or Adult Hits, dating back to 1991 or so.