OK, so we thought we would take a trip to Montana in Mid August with a 35 ft gas MH from Massachusetts. Some have said it is too hilly and some would really be very scary on the brakes and high grade...
One route I have taken several times is cross to Canada at Thousand Islands to Sarnia/Port Huron then up to the Michigan Upper Peninsula over to Fargo ND or Sioux Falls SD then west. Nice scenery with much to see no major traffic problems unless you hit Toronto during rush hour.