There's no missing the spot where the Appalachian Trail ends and the path up Maine's tallest mountain begins: It's where the manicured AT dissolves into a sparse, rocky mountain trail, a straight shot to the top that requires full-body bouldering and quad-burning ascents. "It still feels primitive," says Jennifer Pharr Davis, who holds the Appalachian Trail speed record and details her Katahdin time in her book, 'Called Again.' It feels more like a West Coast hike. An hour into an ascent, at 3,000 feet, you rise above the treeline, and the trail basically becomes a series of boulders and cliffs. At points, you'll need to do pull-ups, especially on Knife Edge, where the path is a few feet wide, with thousand-foot drops on both sides. If you lose your way, just look up.

Getting there: From the Bangor Airport, drive two hours to Mount Katahdin. Reserve ahead for a campsite or bunkhouse at Baxter State Park's Roaring Brook Campground, the most popular trailhead for the mountain.