National Trails System Act (1968)
The National Trails System Act became law October 2, 1968. The Act authorized a national system of trails and defined four categories of national trails: National Scenic Trails, National Historic Trails, National Recreation Trails, and Connecting/Side Trails. The Appalachian Trail and the Pacific Crest Trail were the first long distance hiking trails designated at National Scenic Trails under the Act. In 1978 the Continental Divide Trail (and four others) were added to the roster of National Scenic Trails. Since then, the number of trails with the NST designation has grown to 20.
The specific text referring to the Appalachian Trail reads:
The Appalachian Trail, a trail of approximately two thousand miles extending generally along the Appalachian Mountains from Mount Katahdin, Maine, to Springer Mountain, Georgia. Insofar as practicable, the right-of-way for such trail shall comprise the trail depicted on the maps identified as "Nationwide System of Trails, Proposed Appalachian Trail, NST-AT-101-May 1967", which shall be on file and available for public inspection in the office of the Director of the National Park Service. Where practicable, such rights-of-way shall include lands protected for it under agreements in effect as of the date of enactment of this Act, to which Federal agencies and States were parties. The Appalachian Trail shall be administered primarily as a footpath by the Secretary of the Interior, in consultation with the Secretary of Agriculture.
This final sentence is important, because it gives the Secretary of the Interior supervisory authority over the length of the Appalachian Trail. Prior to the passage of the National Trails System Act, supervisory authority over the Trail was exercised by a network of trail clubs, private landowners, and state and local authorities. By making the Appalachian Trail, in effect, a national park, the Congress took away from this distributed network of actors the ability to make final decisions about the fate of the Trail. Over the coming decades, the National Park Service and the National Forest Service, through a sometimes difficult series of negotiations with the Appalachian Trail Conference (now Conservancy), arrived at a novel public/private partnership relationship for maintaining and overseeing the Trail.