The original NPS Auto Route of the Lewis and Clark National Historic Trail, prior to the Trail's extension by Congress (P.L. 90-543, as amended through P.L. 116-9, March 12, 2019). The most current and up-to-date layer that should be used in place of this dataset is the Lewis and Clark National Historic Trail Congressionally Designated Route referenced here: DataStore - LECL Lewis and Clark NHT Auto Route Final Combined

This data set represents the official National Park Service centerline of the Lewis and Clark National Historic Trail Auto Route as of 2017. The spatial data was created by the National Park Service prior to the extension of the Lewis and Clark National Historic Trail in 2019 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.

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 expedition of Lewis and Clark and the Corps of Discovery. A total of 11 Trail states are connected by the Auto Route in this dataset (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.

The Lewis and Clark National Historic Trail is approximately 4,900 miles long, extending from the Ohio River in Pittsburgh, Pennsylvania to the mouth of the Columbia River in Oregon, following both the outbound and inbound routes of the Lewis and Clark Expedition. The trail connects 16 states (Pennsylvania, West Virginia, Ohio, Indiana, Kentucky, Illinois, Missouri, Kansas, Nebraska, Iowa, South Dakota, North Dakota, Montana, Idaho, Washington, and Oregon) and was established by Congress in 1978 as part of the national trails system (NTS) as one of four original national historic trails. This trail commemorates the 1803-1806 expedition of Lewis and Clark and the Corps of Discovery, which explored the Louisiana Territory and beyond. This epic journey contributed to significant scientific knowledge and profound political, social, economic, cultural, and environmental changes to the lands and the peoples of the North American continent.