The Lewis and Clark National Historic Trail Auto Route is a system of over 6,100 miles of roads and highways bracketing each side of the Lewis and Clark National Historic Trail, which commemorates the 1804-1806 expedition of Lewis and Clark and the Corps of Discovery. A total of 11 Trail states are connected by the Auto Route (Illinois, Missouri, Kansas, Nebraska, Iowa, South Dakota, North Dakota, Montana, Idaho, Washington, and Oregon), and each state designated the roads and highways that make up the Lewis and Clark Auto Route. The Auto Route provides the primary way in which visitors experience the Lewis and Clark National Historic Trail and travel to Trail destinations.As of 2017, this data set represents the official National Park Service centerline of the Lewis and Clark National Historic Trail Auto Route. The spatial data was created by the National Park Service and is derived from layers developed by the Wyoming Geographic Information Science Center as part of the 2009-2010 Lewis and Clark National Historic Trail Auto Route Inventory and Assessment.