One of the longest, long-distance trails in the world. The American Discovery Trail is a coast-to-coast trail about 6,800 miles long and passes through the District of Columbia and 15 states, 14 national parks and 16 national forests. You can hike, run, bike, and even ride a horse along the route. Completion times vary depending on your mode of travel from 390 days hiking to 5 months cycling. A great way to see the country!