If you're travelling between early June and late October, the easiest way to get from Waterton to Glacier National Park, Montana, is through the Chief Mountain border crossing. Between November and the end of May, the next closest port of entry to the USA is at Carway, south of Cardston.
From the Chief Mountain border crossing, it's a spectacular drive south, through the small town of Babb to St Mary. St Mary is at the eastern end of the "Going to the Sun Road", one of the most amazing highlights of Glacier National Park. To truly appreciate the "Going to the Sun Road", you should allow enough time to travel it in each direction. Take a guided tour or use the Park shuttle to experience this spectacular scenic highway.
After completing the road in both directions, you will be back in St Mary. As you are unable to take your RV over the "Going to the Sun Road", you will need to continue your journey around the perimeter of the park to get to your next overnight stop in West Glacier. Allow a couple of hours to get there.
If you're travelling outside of the peak travel months of July and August, we suggest you check to make sure the "Going to the Sun Road" is open before crossing the border into the USA.