Well I have lived in the Chicagoland area for 70 years and just learned we have camping in some of our Forest Preserves. Two even have designated RV sites.
In the spirit of information exchange I just came back from visiting one of the sites in our Southwest suburbs, Oak Forest, IL. It is
Camp Sullivan. I stopped by the office and got some information to pass on and took a few pictures.
Pricing is expensive for electric only, but this IS Chicago. When I get a chance I will check out the other site that has RV sites.
BONUS - The sign in office is literally across the street from one of our hidden gems,
Jack Gibbons. Been there for over 90 years and noted for their steaks and my favorite, stuffed pork chops. Not cheap but definitely worth it.