This data set represents a simplified version of the official National Park Service centerline of the Lewis and Clark National Historic Trail Auto Route for use in the National Park Service NP Map on the Lewis and Clark National Historic Trail website. The spatial data was created by the National Park Service with the assistance of interns from the U.S. Department of State Virtual Student Federal Service program. This layer was derived from roads data using TIGER/Line shapefiles from the U.S. Census Bureau.

The Lewis and Clark National Historic Trail Auto Route is a system of roads and highways bracketing each side of the Lewis and Clark National Historic Trail, which commemorates the 1803-1806 expedition of Lewis and Clark and the Corps of Discovery. A total of 16 Trail states are connected by the Auto Route (Pennsylvania, West Virginia, Ohio, Kentucky, Indiana, Illinois, Missouri, Kansas, Nebraska, Iowa, South Dakota, North Dakota, Montana, Idaho, Washington, and Oregon). Each individual state designated the roads and highways that make up the Lewis and Clark Auto Route in collaboration with the National Park Service. The Auto Route provides the primary way in which visitors experience the Lewis and Clark National Historic Trail and travel to Trail destinations.