March/April Road trip ideas from Chicago
 

Looking for ideas for a road trip from Chicago area. Wisconsin, Washington DC, and Tennessee are out.
We are willing to drive for 600 or 700 miles. Interested in everything, small towns, cities, nature. We have a highschool senior and friend joining us.
Any ideas is appreciated.

It's about 1,000 miles, but what about Denver area/'Rocky Mountin Nat. Park?
Or,about 800 miles, Natchez, Vicksburg, Jackson, MS.?

St Louis is a 5-hour drive and has lots to do - much of it free, and hotels/motels are cheaper than in other large cities. If you've never gone up in the Arch, reserve it for your final day so you can, while up there, see the spots you've already visited. The Old Courthouse, site of slave auctions and the Dred Scott case, is nearby. You didn't say when you were coming; if it's late April/May, take in a Cardinals game at Busch Stadium. (Yeah, I know you're from Chicago...)
In Forest Park, the zoo is good for 1/2 day and is free, and the Art Museum and History Museum are there. Spend half a day at the Missouri Botanical Garden - the Climatron is tropical, Kemper Center has all sorts of plants that grow well indoors with different kinds of light - and they show tests of different types of lawns too.
Ted Drewes for frozen custard. Concretes or sundaes. If you bring a teenager, you may have to make multiple visits there.
Hike to the confluence of the Missouri River with the Mississippi. It's a park and easy hiking.

Another vote for St. Louis. We drove there from Chicago last summer on a whim and had the best time!
Get yourself tickets to the Cardinals if they are in town.

Kentucky could be fun. Within a 6-8 hour range of Chicago, you could do a multi day trip and see Louisville (Slugger Museum, Churchill Downs, Mohammed Ali Center), Lexington (KY Horse Park, Keeneland), Bardstown (My Old Kentucky Home), and Mammoth Cave/Bowling Green area. You could also head southeast from Lexington and visit Berea (artisans/craft galleries) and Cumberland Falls (home of the moonbow). If you really want to get off the beaten path, you could head into Daniel Boone territory and visit Cumberland Gap National Park in the Middlesboro/Pineville area.