Glacier became a national park on May 11, 1910, and the Great Northern Railway soon built hotels and chalets in it, which is why the lodges are Swiss-chalet style. The Going-to-the-Sun Road, finished in 1932 and dedicated in July 1933, then gave drivers a 50-mile way across the Continental Divide. The park had more than 100 glaciers in 1910. By 2015 only 26 were big enough to count as active, so the name is a little ahead of the ice.
What remains is a park of cedar forest, big lakes and sharp peaks, and it is crowded. Glacier National Park gets about three million visitors from May to September, and the best trailheads fill before sunrise. Three days is the right length because the park is long rather than deep. The road alone takes about two hours without stops, and the two sides are two hours apart by highway. Three days gives one area a day with room for one real hike each. Two days turns it into a drive with views. Be honest about the season too: this plan works from roughly July to mid-September, when the road is open, the trails have melted out and the boats run.
Day one is the west side: Apgar, Lake McDonald, the Trail of the Cedars and Avalanche Lake. Day two is the Going-to-the-Sun Road over Logan Pass, then down the east side to St. Mary. Day three is Many Glacier, the park's best hiking valley. Two Medicine and Waterton Lakes in Canada wait under More Time. Read the United States page for visa and travel basics. No weekday matters, because nothing in the park closes on a set day. What matters is a room on the east side for nights two and three, and that is the first thing to book.