I may be too late to the game — sorry about that.
While the buses are (supposed to be) w/c Accessible, only some of the CTA (Chicago Transit Authority) train stations are Accessible (with elevator). Here is an inelegant and cumbersomely written list of those.
If you already went to Chicago I hope you had a marvelous time! We are going mid-October for a long weekend. After, I’ll post all our specifics because we are going Full Tourist.