Congress established the Lewis and Clark National Historic Trail to commemorate the Lewis and Clark Expedition and mark and preserve the route taken by the Corps of Discovery. It stretches approximately 4,900 miles from Pittsburgh, Pennsylvania to the mouth of the Columbia River near Astoria, Oregon. The National Park Service administers the trail, which connects 16 states. The historic trail is not a surface trail like the Appalachian Trail. It consists of a corridor of historic sites along the route of the expedition.