 The Lewis and Clark National Historic Trail , some 3 @,@ 700 miles ( 6 @,@ 000 km ) long , follows nearly the entire Missouri River from its mouth to its source , <unk> the route of the Lewis and Clark Expedition . <unk> from Wood River , Illinois , in the east , to Astoria , Oregon , in the west , it also follows portions of the Mississippi and Columbia Rivers . The trail , which spans through eleven U.S. states , is maintained by various federal and state government agencies ; it passes through some 100 historic sites , notably archaeological locations including the Knife River Indian <unk> National Historic Site . 
