Boulder Pass Trail is a 30.1 mile moderately trafficked point-to-point trail located near East Glacier Park, Montana that features a lake and is rated as moderate. The trail offers a number of activity options and is accessible from March until October.
Classic backpacking shuttle starting in Canada and ending ins US. Can be done in three nights but i recommend four. Make sure you get a chance to stay at Hole-in-the-Wall Campsite; it is definitely one of the most spectacular sites I've ever stayed at.