Mississippi and Missouri Rivers Summary

  • Last updated on November 10, 2022

In addition to draining nearly one-half the continental United States, the Mississippi-Missouri River system was historically the principal transportation artery of the Midwest. It consequently played a major role in facilitating domestic trade and the development of the interior of the United States.

The Mississippi and Missouri Rivers and their many tributaries drain an area of about 1.23 million square miles in the center of the United States. Extending 2,341 miles, the Missouri River is the longest river in the United States. The Mississippi and the Missouri, its principal tributary, together form the fourth-longest river in the world–a system measuring 3,900 miles.Mississippi RiverMissouri River

Two steamboats and a raft navigate the Mississippi River in the 1860’s.

(Library of Congress)

Early in the nineteenth century, the U.S. Army Corps of Engineers began surveying the Mississippi River and its major tributaries, notably the Missouri, Ohio, and Tennessee Rivers. Transportation;Mississippi and Missouri RiversThough the rivers’ potential as a major transportation system was great, the many rapids, sandbars, and other hazards–such as naturally occurring log jams–had to be reduced to make the rivers safely navigable.

Commercial Potential

The potential value of the Mississippi River system as a transportation route for passengers and cargo was recognized by early European explorers. Until the third decade of the nineteenth century, however, that potential was severely limited by the difficulty of moving boats upriver. By the early nineteenth century, large amounts of timber and other heavy cargoes were being floated down the river on rafts, which were dismantled and sold at New Orleans, and on keelboats, which relied on humans using poles to work their slow, tortuous way back upriver. The full potential of the rivers for transportation was realized only after the development of practical steam engines made possible steam-powered boats that could carry cargo and passengers upstream. As expanding steamboat traffic carried goods and settlers up the Mississippi and Missouri Rivers and into their many navigable tributaries, economic development followed. A large portion of the first cities built in the Mississippi River basin naturally arose as riverports.

The first steamboat reached Minneapolis and St. Paul in 1823. During the following decades, the development of the increasingly large and powerful high-pressure Mississippi River Steamboatssteamboats made it necessary to deepen the shallowest stretches of the channel from four to six feet by 1910. Later in the twentieth century, the further evolution of tow boat and barge technology required further deepening to nine feet. As the use of the rivers for logging decreased under the pressures of a growing agricultural economy, and with the railroads offering an economically viable, and more flexible, alternative for shipping bulk products, the Army Corps of Engineers found it necessary to consider the cost-benefit ratio of continuing to improve and deepen the channel. Added to the fundamental issues of profitability were the new concerns about the impact of the system of dams and locks necessary to maintain a deeper channel on the marshes, floodplain area, and meanders that keep a river ecosystem healthy.

Traditionally, the Missouri River delivers high discharge from the early spring to the early summer when the snow melts first in the Midwest and then in the Rocky Mountains. With the intense evaporation of the summer, the low-discharge period extends until December, making traveling on these rivers more treacherous. Although Congress had approved the plans to deepen the Mississippi-Missouri Rivers during the 1920’s, President Herbert Hoover blocked the funding necessary for construction. It was only in 1933, in the midst of the Great Depression, that work began under President Franklin D. Roosevelt. Seven years later, in 1940, the last of the twenty-nine locks and dams was completed and heavier commercial barges began moving upstream, carrying oil, coal, chemicals, fertilizers, and raw materials for the industrial centers of the Midwest, and returning laden with enormous quantities of corn, wheat, and soybeans produced by midwestern farmers. As a further benefit of the project, the lakes formed behind these locks offered new opportunities for recreational fishing and boating.

Flood Control

The Mississippi River system has been plagued with major floods–most notably in 1912, 1913, 1927, 1973, 1993, and 2005. The flood of 1927 was especially severe; more than 200 people lost their lives, and more than 600,000 others had to be evacuated. Moreover, crops were destroyed, and virtually all economic activity was paralyzed for weeks until floodwater receded. As a result of the calamity, Congress passed the Flood Control Act of 1928Flood Control Act of 1928, which funded a new round of ambitious projects aimed at managing floodwaters through improvement and stabilization of the channel, and the construction of new levees and floodways. The most immediately apparent of these projects were the levees, which raised the banks of the rivers above expected flood levels. More than 2,200 miles of levees and floodwalls were built along the Mississippi and tributaries. For almost fifty years, these monumental efforts appeared to control the river.

Despite all these flood-control efforts, the Mississippi River reached its highest level in more than 150 years in the spring of 1973. The stage for the 1973 flood was set during the late fall and winter of 1972, when heavy rainfall all along the river and its tributaries was followed by equally heavy snowfall in the north and west. The month of February, 1973, was unusually warm, and the consequent snowmelt collected in a drainage basin that was already saturated. On March 13, following a warm spell that rapidly melted the snow in the northern part of the drainage basin, flooding conditions were reported on the Missouri River. The flooding was worsened by heavy precipitation, in which some areas of the drainage basin received more than fourteen inches of rainfall in forty-eight hours.

Because the Mississippi River floods annually, the Army Corps of Engineers had previously built a series of structures that would allow the diversion of excess water to the Atchafalaya River, a shorter route to the Gulf of Mexico. Unfortunately, the flood control system was overwhelmed by the magnitude of the event, which was the worst flood in the region since 1927. In the lower Mississippi River valley, 17 million acres were inundated, as well as 600,000 acres in the delta. The flood, which did not completely recede until June, caused more than $180 million in property damage and took a terrible toll on the wildlife living in the delta. More than thirty people died, and thirty-five thousand people were left homeless.

The combination of unusual events that led to the 1973 flood was repeated in 1993. Intense late spring precipitation, twelve inches above normal, fell in the eastern Dakotas, southern Minnesota, Kansas, Wisconsin, Iowa, southern Nebraska, and Missouri. The resulting flood on the Mississippi River and 150 major rivers and tributaries that flow into it caused forty-five casualties and almost $15 billion in property damage. In this event, the water control system was more than overwhelmed; hundreds of levees broke along the Missouri and Mississippi Rivers, severely disrupting both land transportation, by the flooding of highways and destruction of bridges, and barge traffic, for which hazardous waterways made movement impossible for more than seven weeks.

On August 29, 2005, levees and flood walls suddenly failed in New Orleans under the pressure of the storm surge of Hurricane KatrinaHurricane Katrina. This was the worst engineering disaster in United States history. It caused the death of 1,464 people and the collapse of the region’s economic activities.

No river system has had a greater role in the expansion and development of the United States than the Mississippi-Missouri system. With its tributaries, it forms a network of navigable waterways 12,350 miles in length that was the primary route by which the regional economy developed in the nineteenth century. Even in the twenty-first century, this river system remains immensely important, as vessels carry more than 300 million tons of goods on its waters every year.

Further Reading
  • Ambrose, Stephen E., Sam Abel, and Douglas Brinkley. The Mississippi and the Making of a Nation: From the Louisiana Purchase to Today. Washington, D.C.: National Geographic, 2002. The book gives a detailed history of the development of the Mississippi River basin.
  • Barry, John M. The Great Mississippi Flood of 1927 and How It Changed America. New York: Simon & Schuster, 1998. This book traces one of the country’s worst natural disasters.
  • Brinkley, Douglas. The Great Deluge: Hurricane Katrina, New Orleans, and the Mississippi Gulf Coast. New York: HarperCollins, 2007. Thorough study of the economic impact of Hurricane Katrina on New Orleans and the lower Mississippi region.
  • O’Neill, Karen M. Rivers by Design: State Power and the Origins of U.S. Flood Control. Durham, N.C.: Duke University Press, 2006. An examination of river development that looks at both the Mississippi and the Sacramento Rivers. Focuses on the early development of the Mississippi as a waterway.
  • Twain, Mark. Life on the Mississippi. 1883. Facsimile reprint. New York: Oxford University Press, 1996. Classic work on the golden age of steamboating in which Twain recounts his years as a steamboat pilot on the Lower Mississippi during the late 1850’s and describes the immense changes that had taken place when he returned to the river in 1882. Includes chapters on the earlier history of the river and devotes considerable space to the river’s economic impact on the United States.


Colorado River water

Dams and aqueducts

Erie Canal


Hurricane Katrina

Lewis and Clark expedition

Louisiana Purchase

Pike’s western explorations


U.S. Department of Transportation

Water resources

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