Latitude: 49.05 Longitude: -113.90
Waterton Lakes National Park is across the border from Glacier National Park. The latter will simply be called "National Park" once all the glaciers have melted. It is smaller that the U.S. park, but there are choice hikes, lakes for kayaking, and a pleasant village with places to eat and get supplies. We spent a day there kayaking, visiting the old hotel, and hiking the Red Canyon.
You can walk from the Canadian side along the lake, cross the border, and check in with a U.S. official on that side.