When planning my trips I rely on tourism information from the states I plan on visiting. All the information can be obtained along with a road map by checking with the states on line. A simple matter and many states can be contacted in a very short time. I also rely on ideas from the wonderful trip reports in this forum.
The Tahquamenon Falls in MI, Mount Rushmore (be sure to go to the evening program!), Custer State Park, Wind and Jewel Cave National Parks, Badlands National Park (great boondocking on Buffalo Gap National Grasslands just north of the Park), both the North and South Units of Theodore Roosevelt National Park (Cottonwood Campground - last time I was there a herd of Bison moved through the campground at 5:00AM),Fort Union Trading Post and Fort Buford in North Dakota near the confluence of the Yellowstone and Missouri Rivers. These are just a few on the places I have found in the areas you mention. There are also two nice museums in the Dover, Ohio area (Warther train carvings and also another Warther Museum with ships carved in ivory)
Hope this helps.
Grant