The National Trails System is a series of trails in the United States designated "to promote the preservation of, public access to, travel within, and enjoyment and appreciation of the open-air, outdoor areas and historic resources of the Nation". There are four types of trails: the national scenic trails, national historic trails, national recreation trails, and connecting or side trails. The national trails provide opportunities for hiking and historic education, as well as horseback riding, biking, camping, scenic driving, water sports, and other activities. The National Trails System consists of 11 national scenic trails, 21 national historic trails, over 1,300 national recreation trails, and seven connecting and side trails, as well as one national geologic trail, with a total length of more than 91,000 mi (150,000 km). The scenic and historic trails are in every state, and Virginia and Wyoming have the most running through them, with six.

The Appalachian Trail, also called the A.T., is a hiking trail in the Eastern United States, extending almost 2,200 miles (3,540 km) between Springer Mountain in Georgia and Mount Katahdin in Maine, and passing through 14 states. The Appalachian Trail Conservancy claims the Appalachian Trail to be the longest hiking-only trail in the world. More than three million people hike segments of the trail each year.