A lot of good info here. Don't forget the Mitchell SD Corn Palace!!! You have a lot of KOA campgrounds going west from WI and are great for big miles days, just wanting a tent site and shower. One east of Yellowstone at Cody, another at West Yellowstone, another north of Beartooth Pass at Red Lodge......just in case. As indicated, state and national parks tend to fill early. I have run this trip from WI(Manitowoc) and Fl. Wonderful trip. Expect cold camping nights. Avoid holiday weekends if you can. Have fun. jr