The National Trails System Act of 1968 created three types of national trails, "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." The three trail types were National Scenic Trails and National Recreation Trails, along with associated side and connecting trails. Two of the most important of the National Scenic Trails were the Appalachian Trail (AT) and the Pacific Crest Trail (PCT). Eventually in 1978, a fourth category of trail, National Historical Trails, was added to those protected by the Act. This Act is the foundation stone of federal oversight of the Appalachian Trail, the Pacific Crest Trail, and other long distance trails such as the Continental Divide Trail.