We travelled from MI to Yellowstone, Jackson Hole, etc. last September/October. Many have already shared great tips like Grizzly RV Park and Yellowstone visitation strategies. Our route took us north across the Mackinac Bridge, then west across upper MN, which was just stunning in their vast glades of prairie grass and related ecosystems. I highly recommend making time to stop at Theodore Roosevelt NP in Medora, ND. What we experienced was a total surprise, and in a very, very good way. Work your way to Cody, then take a day and drive the Chief Joseph Scenic Highway north of town, but NOT in your MH!. This has to be one of the most beautiful drives on our good planet. Soak in one of the many hot pools in Thermopolis. Take as many state highways as you possibly can, and enjoy the real America.
Have a blast!