Last year we started our visit to these places from Salt Lake City. Took US 89 from I-15 at Brigham City. On the way, in Montpelier, ID is a really neat place to visit, the
Oregon Trail Center. Would advise calling ahead for tour reservations. There is lots of RV parking.
Stayed at
The Virginian RV Resort in Jackson, WY.
At Yellowstone, you probably could find a spot in the Fishing Bridge CG, but lots of people rave about
Grizzly RV Park in West Yellowstone.
From West Yellowstone we used US 287, I-90, US 93 and US 2 to West Glacier. Stayed at W. Glacier KOA which was very nice and close to the NP entrance. Plan for a full day when you do the Going to the Sun highway. You'll want to make many stops to enjoy the sights!
Enjoy your trip!
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'05 Itasca Suncruiser 38R, '04 Saturn VUE
BlueOx Towing Pkg, WH W24, UltraPower Upgrade
49 States & 7 Provinces visited in MH| WIT W112365