Bug City was Second Edition, but it is BY FAR the best resource on Chicago. I wouldn't even bother with
Feral Cities (To be clear, while I made sure it followed FC continuity, I spent FAR more time using
Bug City as a resource when I wrote the Chicago-set adventure in
Artifacts Unbound [Mainly in that I corrected the gross omission of the mile-high Truman Tower and references to the Chicago Core as it was known in mid-21st century Chicago, which is literally 15 miles south of the RL Loop, aka Downtown/SR Noose]. Actually the Core was bisected by the southern CZ wall).
Target: UCAS, which is also Second Edition, is what establishes post-CZ Chicago as basically being ... CZ Chicago, but with the Wall unmanned (not even gone).
Since then, some people have had the balls to move in and try and set up shop. Others just feed stuff for the stupendous badasses who remained to continue playing out Mad Max of the Midwest.
Then we have
Dirty Tricks, which just came out, which establishes that the Illinois governor has finally seemed to tip the fulcrum towards a real push to rebuilding Chicago.
Which will lead into Missions Season 5 being set in Chicago, and who knows what next. Well, Bull does.