Humanities › Geography The Jefferson-Mississippi-Missouri River System The Fourth Largest River System in the World Drains Much of North America Share Flipboard Email Print The Gateway Arch is seen as the flooding Mississippi River runs in front of it June 25, 2008 in St. Louis, Missouri. Joe Raedle/Getty Images Geography Physical Geography Basics Political Geography Population Country Information Key Figures & Milestones Maps Urban Geography By Colin Stief is an experienced project manager for environmental organizations. He holds a master's degree in environmental management from Duke University. our editorial process Colin Stief Updated January 21, 2020 The Jefferson-Mississippi-Missouri River system is the fourth largest river system in the world and serves transportation, industry, and recreation as the most important inland waterway in North America. Its drainage basin collects water from 41% of the contiguous United States, covering a total area of more than 1,245,000 square miles (3,224,535 square kilometers) and touching 31 U.S. states and 2 Canadian provinces in all. The Missouri River, the longest river in the United States, the Mississippi River, the second longest river in the United States, and Jefferson River combine to form this system at a total length of 3,979 miles (6,352 km). (The Mississippi-Missouri River combined is 3,709 miles or 5,969 km). The river system begins in Montana at the Red Rocks River, which quickly turns into the Jefferson River. The Jefferson then combines with the Madison and Gallatin Rivers at Three Forks, Montana to form the Missouri River. After winding through North Dakota and South Dakota, the Missouri River forms part of the boundary between South Dakota and Nebraska, and Nebraska and Iowa. Upon reaching Missouri state, the Missouri river joins up with the Mississippi River about 20 miles north of St. Louis. The Illinois River also joins with the Mississippi at this point. Later, in Cairo, Illinois, the Ohio River joins the Mississippi River. This connection separates the Upper Mississippi and the Lower Mississippi, and doubles the water capacity of the Mississippi. The Arkansas River flows in to the Mississippi River north of Greenville, Mississippi. The final junction with the Mississippi River is the Red River, north of Marksville, Louisiana. The Mississippi River eventually splits up in to a number of different channels, called distributaries, emptying into the Gulf of Mexico at various points and forming a delta, a triangular shaped alluvial plain composed of silt. About 640,000 cubic feet (18,100 cubic meters) is emptied in to the Gulf every second. The system can easily be broken in to seven different basin regions based on the major tributaries of the Mississippi River: Missouri River Basin, Arkansas-White River Basin, Red River Basin, Ohio River Basin, Tennessee River Basin, Upper Mississippi River Basin, and Lower Mississippi River Basin. The Formation of The Mississippi River System More recently, about two million years ago, glaciers upwards of 6,500 feet thick repeatedly encroached upon and retreated from the land. When the last ice age ended approximately 15,000 years ago, massive quantities of water were left behind to form the lakes and rivers of North America. The Jefferson-Mississippi-Missouri River system is just one of the many water features that fill the giant swath of plain between the Appalachian Mountains of the east and the Rocky Mountains of the West. History of Transportation and Industry on the Mississippi River System Beginning in the early 1800s, steamboats took over as the dominant mode of transportation on the river ways of the system. Pioneers of business and exploration used the rivers as a means of getting around and shipping their products. Beginning in the 1930s, the government facilitated the navigation of the system’s waterways by building and maintaining several canals. Today, the Jefferson-Mississippi-Missouri River System is used primarily for industrial transportation, carrying agricultural and manufactured goods, iron, steel, and mine products from one end of the country to the other. The Mississippi River and the Missouri River, the two major stretches of the system, see 460 million short tons (420 million metric tons) and 3.25 million short tons (3.2 million metric tons) of freight transported every year. Large barges pushed by tugboats are the most common way of getting things around. The immense commerce that takes place along the system has fostered the growth of countless cities and communities. Some of the most important include Minneapolis, Minnesota; La Crosse, Wisconsin; St. Louis, Missouri; Columbus, Kentucky; Memphis, Tennessee; and Baton Rouge and New Orleans, Louisiana. Concerns Dams and levees are the most common guard against destructive floods. Important ones along the Missouri and Ohio Rivers limit the amount of water that enters the Mississippi. Dredging, the practice of removing sediment or other material from the bottom of the river, makes the rivers more navigable, but also increases the amount of water the river can hold – this poses a bigger risk for flooding. Pollution is another distress to the river system. Industry, while providing jobs and general wealth, also produces a large amount of waste that has no other outlet but in to the rivers. Insecticides and fertilizers are also washed away in to the rivers, disrupting ecosystems at the point of entry and further down stream as well. Government regulations have curbed these pollutants but pollutants still find their way in to the waters.