To add a few more - Joliet, Aurora, Palwaukee, Kenosha, Du Page.
Wherever you end up flying from, you are only an hour or so (flying time) from Oshkosh. I think both the FBO's can be persuaded to take you to the museum, which is on the south west side of the field. If you time your visit over a weekend, in May, Pioneer Airport will be open. Try
www.airventuremuseum.org If the weather is cooperating, you could find that the 1929 Ford Tri Motor, the Travel Air E-4000, the Spirit of St Louis replica or the Bell 47 are out to play and all four can carry paying passengers. Phone ahead first to check as some of the aircraft may be out on tour, or there may not be pilots available to fly them.
If you do decide to visit Oshkosh, pm me.
I would also recommend a visit to Poplar Grove to see how the other half live
Its a gorgeous airpark - hangar your plane under or beside the house type of thing - with a lovely selection of unique aircraft based on the field.