Missouri River

The Missouri River is the longest river in the United States. It flows through the Central and Mountain West regions of the country. The river starts high in the Rocky Mountains of southwestern Montana. From there, it travels east and south across the Great Plains. Eventually, it enters the Mississippi River north of St. Louis, Missouri.

When the Missouri joins the Mississippi, they form a massive system. This combined system is the fourth-longest river system in the world. The Missouri is even longer than the Mississippi itself. However, the Mississippi carries a larger volume of water.

The river drains a massive area called a watershed. This watershed covers more than 500,000 square miles. That is about one-sixth of the total area of the United States. The watershed includes parts of ten U.S. states and two Canadian provinces.

It stretches from the Rocky Mountains to the Mississippi River Valley. The watershed is roughly the same size as the Canadian province of Quebec. It contains about one-fourth of all agricultural land in the United States. This land produces over one-third of the nation's wheat, flax, barley, and oats.

The river begins through the meeting of three different streams. The longest source stream starts near Brower's Spring in Montana. It flows through the Red Rock and the Beaverhead River. This stream eventually joins the Big Hole to form the Jefferson River. Other streams come from Yellowstone National Park in Wyoming. These include the Firehole River and the Gallatin River.

The official Missouri River starts where the Jefferson and Madison rivers meet. This happens at Missouri Headwaters State Park near Three Forks, Montana. The Gallatin River joins the main stem just one mile downstream.

As the river flows, it passes through many different landscapes. It moves through the Missouri Breaks, which are canyons and badlands. The river also passes through many large man-made lakes. These are called reservoirs.

Large dams were built to create these reservoirs. These structures help with irrigation, flood control, and making electricity. Fifteen dams sit on the main stem of the Missouri River. Hundreds of other dams exist on its many tributaries. Some of the largest artificial lakes in the U.S. are here. These include Lake Sakakawea, Lake Oahe, and Fort Peck Lake.

Humans have lived near this river for a very long time. For over 12,000 years, Native Americans used the river for food and travel. More than ten major groups lived in the watershed. Most of these groups were nomadic, meaning they moved from place to place. They relied on huge herds of bison that lived on the Great Plains.

Europeans first encountered the river in the late seventeenth century. The land passed through Spanish and French hands. Later, the United States acquired the region through the Louisiana Purchase. In the 1800s, the river became a path for westward expansion. Trappers used it for the fur trade.

Later, pioneers used steamboats to travel west.

The weather in the watershed changes a lot. It has a continental climate. This means it has warm, wet summers and very cold, harsh winters. Most of the area gets an average of 30 inches of rain each year. However, some parts of the Rockies get much more. In the winter, temperatures in the north can drop to -40 degrees Fahrenheit. In the summer, temperatures can rise above 100 degrees Fahrenheit.

These extreme changes affect the plants and animals in the region.

Many large cities are located within the Missouri River basin. Denver, Colorado, is the largest city in the watershed. It has a population of more than 600,000 people. Other major population centers include Omaha, Nebraska, and Kansas City, Missouri. The St. Louis area is also a major center near the river's end. While some areas are crowded, the northwestern part of the basin is very empty. Today, the river is very important for industry and farming. However, heavy development has changed the water quality. It has also impacted the fish and wildlife populations in the area.