<P> 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, retracing the route of the Lewis and Clark Expedition . Extending 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 Villages National Historic Site . </P> <P> Parts of the river itself are designated for recreational or preservational use . The Missouri National Recreational River consists of portions of the Missouri downstream from Fort Randall and Gavins Point Dams that total 98 miles (158 km). These reaches exhibit islands, meanders, sandbars, underwater rocks, riffles, snags, and other once - common features of the lower river that have now disappeared under reservoirs or have been destroyed by channeling . About forty - five steamboat wrecks are scattered along these reaches of the river . </P> <P> Downstream from Great Falls, Montana, about 149 miles (240 km) of the river course through a rugged series of canyons and badlands known as the Missouri Breaks . This part of the river, designated a U.S. National Wild and Scenic River in 1976, flows within the Upper Missouri Breaks National Monument, a 375,000 - acre (1,520 km) preserve comprising steep cliffs, deep gorges, arid plains, badlands, archaeological sites, and whitewater rapids on the Missouri itself . The preserve includes a wide variety of plant and animal life; recreational activities include boating, rafting, hiking and wildlife observation . </P> <P> In north - central Montana, some 1,100,000 acres (4,500 km) along over 125 miles (201 km) of the Missouri River, centering on Fort Peck Lake, comprise the Charles M. Russell National Wildlife Refuge . The wildlife refuge consists of a native northern Great Plains ecosystem that has not been heavily affected by human development, except for the construction of Fort Peck Dam . Although there are few designated trails, the whole preserve is open to hiking and camping . </P>

Where do the yellowstone and missouri rivers meet