Missouri River Valley

The Missouri River Valley outlines the journey of the Missouri River from its headwaters where the Madison, Jefferson and Gallatin Rivers flow together in Montana to its confluence with the Mississippi River in the State of Missouri. At 2,300 miles (3,700 km) long the valley drains one-sixth of the United States, and is the longest river valley on the North American continent. The valley in the Missouri River basin includes river bottoms and floodplains.

The Missouri's valley ranges from 6 miles (9.7 km) to 10 miles (16.1 km) wide from edge to edge, with gentle slopes from the adjacent upland to the valley floor. Other segments are narrow, less than two miles (3 km) wide, with rugged valley sides. Generally, the wide segments trend west-east and the narrow segments trend north-south.

Starting in the state of Montana, the Missouri River Valley travels through North Dakota, South Dakota, forms the shared border of eastern Nebraska and western Iowa, goes into Kansas and then eastward through the state of Missouri. The valley travels through several distinct ecoregions with distinct climate, geology and native species.

The Loess Hills are a unique geographic feature of the valley. Loess, a wind-deposited soil, is compounded in slowly rising hills at various points in extreme eastern portions of Nebraska and Kansas along the Missouri River Valley, particularly near the Nebraska cities of Brownville, Rulo, Plattsmouth, Fort Calhoun, and Ponca, rising no more than 200 feet (61 m) above the Missouri River bottoms. The majority of these hills stretch along the east side of the river, from Westfield, Iowa in the north to Mound City, Missouri in the south.

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