Lewis and Clark National Historic Trail

Series of trails, highways, river routes, and selected sites marking the route of the Lewis and Clark expedition 1804–06, led by US government surveyors Meriwether Lewis and William Clark. Running from St Louis, Missouri to the mouth of the Columbia River, the trail is 7,200 km/4,500 mi long and passes 500 historic sites; it was formally inaugurated in 1978.

The expedition's westward journey from St Louis followed the Missouri and Jefferson rivers, crossed the Continental Divide through Lemhi Pass, and descended the Clearwater and Snake rivers to reach the Columbia; their travels ended on the Pacific coast at Fort Clatsop, Oregon. On the return journey to St Louis they explored the Marias and Yellowstone rivers.