The last 100 miles of the 2,181-mile-long Appalachian Trail in Northern Maine are by far the most extreme – a 10-day trek that's unparalleled in remoteness and difficulty. The elevation on this hike is ever-changing, stream crossings are constant, and the mud is inescapable. "It's a full-contact hike," says Philip Pepin, the owner of 100 Mile Wilderness Adventures. "There are ledges and paths with house-size boulders that require more climbing than hiking." So you'll want to pack light. For $100, Pepin offers a full resupply at the 54-mile mark, as well as a ride to and from Bangor, Maine (about 80 miles away), and emergency support. It's peace of mind you'll want when hiking in a region that has more moose than roads, and not a person living for miles in any direction. "You don't see houses or farms or man-made structures anywhere," Pepin says. "You feel removed from man's impact." []