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Missouri RiverBritannica Elementary Article

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At 2,315 miles (3,726 kilometers), the Missouri River is nearly as long as the Mississippi River, into which it flows. Together the Missouri and the Mississippi form one of the world's longest river systems. From the beginning of the Missouri, high in the Rocky Mountains, to the mouth of the Mississippi, at the Gulf of Mexico, is a distance of 3,710 miles (5,971 kilometers). Only three rivers in the world are longer.


Physical features

The Missouri River drains 529,000 square miles (1,370,000 square kilometers) of North America. This includes 15 percent of the land area of the United States (not counting Hawaii and Alaska). The drainage area includes a small part of southern Canada as well.

The Missouri River begins in southwestern Montana, at the spot where the Jefferson, Madison, and Gallatin rivers come together. The Missouri first flows north and then turns eastward. It is a fast-flowing river at this point in its course. Near the city of Great Falls, Montana, the Missouri drops more than 400 feet (122 meters) over a series of five waterfalls.

After leaving Montana, the Missouri flows more slowly. Its course takes it gradually southeastward, either through or along the borders of North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri. The river finally reaches its mouth just north of St. Louis, Missouri. There it joins the Mississippi. The most important rivers that flow into the Missouri include the Yellowstone River in North Dakota, the Cheyenne River in South Dakota, the Platte River in Nebraska, and the Kansas River in Kansas.

Before dams were built, the Missouri carried a huge amount of soil throughout its course. The water was brown, and the river was nicknamed the Big Muddy. Today, however, dams trap much of the soil in the upper part of the river. This has left the lower part of the river cleaner.



Barges pushed by tugboats move cargo on the Missouri River between Sioux City, Iowa, and the river's mouth. Dams stop barge traffic from going farther north than Sioux City. The barges carry corn, soybeans, and wheat from farms in the area. They also transport fertilizer, cement, and asphalt. Omaha, Nebraska, and Kansas City, on the Missouri-Kansas border, are the main ports along the river's course. During the winter, the river is usually closed to barge traffic for four months because of ice.

There are seven major dams and dozens of smaller dams on the Missouri. The dams use water from the river to produce electricity. They also create reservoirs, or artificial lakes, behind them. The reservoirs store water that is needed for cities and for irrigation of crops. Irrigation is important because most of the region around the river has a fairly dry climate.

The Missouri also supports a large recreation industry. People use the reservoirs for fishing and boating, and sandbars along the river serve as beaches.


History and exploration

The Missouri River was named after a Native American people called the Missouri. The Missouri and many other Native American tribes used the river for travel and trading.

The first Europeans to see the mouth of the river were the French explorers Jacques Marquette and Louis Jolliet, in 1673. French fur traders traveled upstream in the 18th century.

The United States bought almost all the land drained by the Missouri in the Louisiana Purchase of 1803. At the time nothing was known about the source or the length of the river. These and many other questions were answered by the U.S. explorers Meriwether Lewis and William Clark. Their expedition traveled up and down the river between 1804 and 1806. In 1819 the first steamboat traveled on the river. Until railroads were built in the 1850s, settlers moving west often went by steamboat along the river at least as far as St. Joseph, Missouri.


Environmental issues

In addition to producing electricity, the dams on the Missouri are also used to control the water level of the river. Sometimes water is held back to prevent floods. At other times water is released to keep the water level high enough for barges to float downstream.

By changing the natural flow of water in the Missouri, dams and reservoirs have altered the river's ecosystem. They have affected the depth and temperature of the water in different parts of the river. Such changes have made it difficult for some species, or types, of plants, animals, and fish to survive. A few wildlife species in the region are now endangered.