When Lewis and Clark began their exploration in 1804, the Missouri River was a wild river with constantly changing channels and chutes. The Big Muddy got its name from its shifting bottom. Every spring, the river topped its banks and deposited nutrients in the floodplain, creating a diverse system of plants and animals. In 1912, Congress funded improvements on the Missouri, and the Army Corps of Engineers was assigned the task. The river was straightened and narrowed for navigation, flood control, farming, economic development, and job creation. The Corps built six large reservoirs to control flooding, removed snags, and used wing dams to direct the broad river into a narrower, deeper, and faster channel for navigation. Today the Missouri is very different from the river Lewis and Clark explored. The entire portion bordering Iowa has been straightened, more than 96 square miles of floodplain have been converted, and the river is 18 miles shorter. More than a third of the river upstream from Iowa is confined in six reservoirs. Thirty thousand acres of sandbars and islands disappeared, along with 17,000 acres of surface water. These changes also transformed the surrounding land. More land was cultivated, while tree cover, wetlands, sandbars, and grasslands disappeared. Reduced fish and wildlife populations reflect the decline in habitat, and many plant and animal species became endangered or threatened, while some disappeared completely.