If you don't mind driving 60 miles into the city, stay at Sycamore RV park in Sycamore, IL. It is just about a 1/4 mile north of Hwy 64 and a right turn (to the east) off Hwy 23. Sits behind the large grain storage operation and the turn in street can be hard to spot the first time, but the park has sites in the trees, on open well drained and flat ground with views of two private lakes. You can fish there, canoe, hike around the lakes, or even walk to downtown Sycamore for great Mexican and Italian food.
New wash rooms and laundry now also open at the park. Great public golf course nearby as well as a super driving range with miniature golf and batting cages. Pretty cold at this time of year, but during the other three seasons Sycamore RV is a quiet, friendly, fun place to stay.
Chicago is about 1 1/2 hours to the loop from Sycamore.