My wife and I have camped in almost EVERY state park and State Recreation area in Indiana (except for 4... which we have visited, but never camped there before, so this next summer we are scheduling those State Parks). I say this because we have not been in any bad State Park or State Recreation area anywhere in Indiana. All of them are great! Pick your choice!
Wisconsin has some really nice State Parks too. Places like the Wisconsin Dells has so much activity, you will come home stone broke! Take lots of money!
One year, for our "big" vacation of the year, we started in Southern Indiana, stayed about 3 nights, then moved to the Central Western part of Indiana and stayed for about 3 nights, then moved to Northern Indiana and stayed for 3 or 4 nights. What were we doing? We searched out Rail Road museums and decided to visit all 7 Rail Road museums in Indiana. We also rode the train at Connersville, French Lick, and Noblesville on that trip. It was quite a fun time. I was into the model railroading at that time, and this gave us actual destination points and activities. It worked out fantastic for us.
What I'm saying is ... if you have a special hobby, or a special interest, maybe you could run a circuit similar to what we did. Your interests might be miniature doll houses, or maybe base ball museums, or race car tracks, or you might be interest in the Civil War, or anything like this. Search your area of interest, see what's located geographically, plot a route, and then look for campgrounds in the area. The Mid West has a lot of STUFF!
How about ghosts? Haunted houses? UFO sitings.
Here's one for you .... "Weird Illinois" or "Weird Indiana" (the series of books).
After we did the train museums, I stumbled into the book called "Weird Indiana". It jam packed full of oddities, like the gigantic pink elephant holding a martinee glass with his truck on Pendleton Pike (Highway 67) east of Indianapolis, or the Masonic Lodge in Indianapolis with the lodge number 666, or the rotating round jail, or the motel that some deranged fellow decided to rent a room, built his own gillitene, drugged himself up, and let his invention chop off his head! I mean "Weird Indiana" is a great book. We keep in the camper all the time now, and when going to a different campground, I pull it out and see if anything is within a reasonable drive. I'm hoping to eventually see everything in that book. The "Weird America" series are a great guide if you run out of places or things to do or see.
Ghost stories and UFO sighting are fun too. Too many take it too serious, but if you go with a light-hearted attitude, it's really a lot of fun. There are books gallore on these subjects and locations.
What I'm sayin' is, pick an area of interest, and try running a circuit. You'll have a blast!