You may notice that the route I posted below has a diversion to take us to British Columbia Highway 93 and US Route 93. There is a reason for that. When Ron and I took the U-Haul down, we wanted to follow Alberta Highway 2 and cross where it becomes US Route 89. This seemed like a good combination of not too many extra miles and a fairly straight and flat road. We had debated it a good bit and come to this conclusion. Then we'd swing around the east side of Glacier National Park and end up in Kalispell. This is the route that Google Maps proposes.
But...after driving for 21 straight hours, when we got to this border crossing at 7:10 a.m., the US Border Patrol wouldn't let us cross. They didn't like our choice of route and didn't think it made sense to them. As they didn't have an X-Ray machine at that particular crossing, they told us we had to go to one of the two in the "area" that did. We we drove an extra 187 miles to the nearest crossing to the west, where we had no problem getting through (and they didn't X-Ray our truck). This trip, Laura and I are just heading for the crossing to begin with, it's a beautiful drive and takes us straight into Kalispell.