The Missouri River, America’s longest river at more than 2,341 miles, flows from the Rocky Mountains through Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri before joining the Mississippi River in St. Louis. In 1804, Lewis and Clark encountered a wild river corridor of prairie, floodplain, forest, water, sand, sky, and mosquitoes, where the fast, shallow, wide river constantly shifted sandbars, carved riverbanks, dropped trees into the water, and carried heavy sediment loads that gave it the nickname "Big Muddy." Since then, natural change and human alteration have transformed the river and its floodplain. The mix of prairie and forest along its banks is nearly gone, and the river’s once highly variable flows have been evened out by dams, reservoirs, levees, and channel narrowing. The lower Missouri River is now confined to a bank-stabilized channel that is much narrower, substantially deeper, and probably even faster than the river Lewis and Clark knew, while these changes and other landscape development have caused drastic declines in animal populations that depended on the river’s natural flood cycles. Conservation efforts by the U.S. Fish and Wildlife Service, other government agencies, and conservation groups now seek to restore and rehabilitate some former channels and floodplain habitats, including floodplains and wet prairies, to mimic wildlife habitats lost or affected by channelization.