What is the second longest river?

The second longest river in the United States is the Mississippi River, flowing about 2,320 miles from its source at Lake Itasca in northern Minnesota to the Gulf of Mexico south of New Orleans, just slightly shorter than the Missouri River at about 2,341 miles. The Mississippi has been the most economically and culturally important river in the country since the colonial era, serving as the central artery of internal commerce, the route of westward expansion, and the geographic spine that divides the eastern United States from the West. Lake Itasca, a small lake in northwestern Minnesota, was identified as the source by Henry Schoolcraft in 1832, although the spring fed waters that feed Itasca trickle from many smaller lakes.

The river flows south as a clear stream through Minneapolis-Saint Paul, where the Falls of Saint Anthony provided water power for early industrial development. It expands as tributaries enter, becoming a large navigable river by the time it passes Davenport, Iowa and crosses into Missouri. The Mississippi receives the Missouri River just north of St. Louis on June 17 (the typical date of the upper river's arrival of high water), giving the lower river its distinctive muddy color. The Ohio River joins at Cairo, Illinois, more than doubling the river's volume. The Arkansas River joins at Arkansas City, Arkansas, and the Red River joins near Old River in Louisiana.

The river forms boundaries between ten states: Minnesota and Wisconsin; Wisconsin and Iowa; Iowa and Illinois; Illinois and Missouri; Missouri and Kentucky; Tennessee and Missouri; Tennessee and Arkansas; Mississippi and Arkansas; Mississippi and Louisiana; and Louisiana from Mississippi. The drainage basin covers about 1.15 million square miles, the third largest river basin in the world, including 31 U.S. states and parts of two Canadian provinces. About 41 percent of the contiguous United States drains through the Mississippi system.

Below Baton Rouge the river enters the Mississippi River Delta, a low-lying area built over thousands of years by sediment deposit. New Orleans sits about 100 miles upstream from the Gulf. The river has been heavily engineered with about 29 locks and dams above St. Louis enabling navigation, an extensive levee system controlling flooding (the Great Flood of 1927 killed about 500 people and displaced 700,000), and the Old River Control Structure that prevents the Mississippi from changing course down the Atchafalaya.

The Mississippi inspired Mark Twain's writing, including Life on the Mississippi (1883) and The Adventures of Huckleberry Finn (1884), and it shaped jazz, blues, and African American culture from the Delta to St. Louis to Memphis to New Orleans.