Land and Water Conservation Fund in the context of Old Erie Canal State Historic Park

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.

In response to a call by President Lyndon B. Johnson to have a cooperative program to build public trails for "the forgotten outdoorsmen of today" in both urban and backcountry areas, the Bureau of Outdoor Recreation released a report in 1966 entitled Trails for America. The study made recommendations for a network of national scenic trails, park and forest trails, and metropolitan area trails to provide recreational opportunities, with evaluations of several possible trails, both scenic and historic. The program for long-distance natural trails was created on October 2, 1968, by the National Trails System Act, which also designated two national scenic trails, the Appalachian Trail and the Pacific Crest Trail, and requested that an additional fourteen trail routes be studied for possible inclusion. Sponsored by Senators Henry M. Jackson and Gaylord Nelson and Representative Roy A. Taylor, part of the bill's impetus was threats of development along the Appalachian Trail, which was at risk of losing its wilderness character, and the Land and Water Conservation Fund was used to acquire lands. In 1978, as a result of the study of trails that were most significant for their historic associations, national historic trails were created as a new category with four trails designated that year. Since 1968, over forty trail routes have been studied for inclusion in the system.