This is the North Country Trail, one of 11 National Scenic Trails in the United States, and the largest NST at about 4600~ miles long. 

This route is special because of the many states it not only goes through but the vastness of the trail and the ecosystems that it crosses through on its more than 4600 mile long route. The consistency to hold high mile days for months on end, lends this route to be for those who want to test themselves physically and more so mentally for months on end, day after day.