The border crossing at Montana Route 17 and Alberta Highway 6 is quick because there is almost no traffic. But you will encounter a grouchy Canadian Customs official intent on sleeping if you pass before 8:00 am.
Waterton National Park
It's a short 41 mile (66 km) drive from St. Mary Lodge to Waterton Park in Alberta. It will take you about an hour to make the trip, which involves dodging cows, horses, and moose along the road.