Continental Divide Trail

The Continental Divide Trail is the longest of America's "Triple Crown" thru-hikes — 4,870 km along the Continental Divide of the Americas from the Mexican border in southern New Mexico to the Canadian border at Glacier National Park, traversing five states (New Mexico, Colorado, Wyoming, Idaho, Montana). It's the highest, longest, and most remote of the three; only 100–200 hikers complete it each year, compared with 800 PCT finishers and ~750 AT finishers.

The CDT is famously "not a trail but an idea" — there's no single waymarked corridor, but a choose-your-own-route network of official trail, alternate routes, and cross-country sections that thru-hikers piece together with a GPS app and a notebook. The trail's character changes by section: the dry desert and lava fields of New Mexico (the trail crosses the Gila Wilderness via a popular off-route variant), the high-altitude Colorado Rockies (the CDT spends 800 km above 3,000 m, more than any other US trail), Wyoming's Great Basin (a 200 km cattle-trail and dirt-road traverse where water is scarce), the wild Wind River Range and Yellowstone, the long Idaho-Montana border ridge, and the dramatic finish in Glacier National Park.

CDT thru-hikers travel northbound (NOBO) from mid-April to late September. There's no single permit; the trail uses CDT Coalition signage and local agency permits (Glacier requires a backcountry permit, Yellowstone requires a permit for any backcountry camping, etc.). Snow timing is everything: start too early and Colorado is impassable; start too late and Glacier closes before you reach it. Resupply is harder than the PCT or AT — towns are 7–10 days apart in many sections and some require hitchhiking from remote highway crossings. The trail is well-documented through the FarOut app, Guthook's commercial map, and the CDT Coalition's free maps. Most hikers consider this the "expert" American thru-hike — best attempted after one of the other Triple Crown trails.