The Lewis and Clark National Historic Trail is approximately 4,900 miles (7,900 km) long, extending from Pittsburgh, Pennsylvania to the mouth of the Columbia River, near present-day Astoria, Oregon.

It follows the historic outbound and inbound routes of the Lewis and Clark Expedition as well as the preparatory section from Pittsburgh, Pennsylvania to Camp Dubois at Wood River, Illinois.

A highway driving route approximates the path taken by the Lewis and Clark Expedition in 1804–06, between St. Louis, Missouri and the Pacific Ocean at Astoria, Oregon.

[3] In 1948 the National Park Service proposed a "Lewis and Clark Tour-way" along the Missouri River from St. Louis to Three Forks, Montana.

[5] From 2003 to 2006, the National Park Service commemorated the bicentennial of the Lewis and Clark Expedition with the Corps of Discovery II traveling exhibit.