Locks and dams

Since the days of the Indian canoe, the Mississippi river has served as a great water highway, linking the heartland of America with the rest of the world. Early in the nineteenth century, the federal government began assuming responsibility for maintaining the nation's waterways for boat traffic. Although the Lower Mississippi River was navigable in all seasons, the Upper Mississippi River was much more unreliable, and during long dry spells many parts of the river were too shallow for large boats. 

In 1930, Congress directed the Army Corps of Engineers to develop and maintain a 9-foot deep, 400-foot wide navigation channel on the Upper Mississippi between St. Louis, Missouri, and St. Paul, Minnesota. To accomplish this, a system of 29 locks and dams was built, most between 1930 and 1940. Each dam creates a lake-sized pool of water above it to maintain the 9-foot channel. Locks adjacent to the dams raise river traffic to the upriver pool or lower it to the downstream pool. The lift in the locks varies from 5.5 feet to 49.2 feet. The dams used in this system are not for flood control, they exist solely to maintain a deep, navigable channel.

The lock and dam system acts as a stairway along the upper river; lowering the river about 420 feet over the 699 miles between St. Paul and St. Louis.  Below St. Louis, the river is deep enough for a barge traffic in its natural state. Each lock area has observation areas where visitors can watch the fascinating locking procedure.

River barges

Mississippi River towboats push rather than pull their tows. Today's powerful diesel towboats move enormous quantities of freight along the river. Tows comprised of 12 to 15 barges carrying up to 22,500 tons of freight are common on the upper river.

An average of 175 million tons of freight moves on the Upper Mississippi each year. The largest tonnage item moved is grain: corn, wheat, oats, barley and rye. Loaded onto barges from riverside elevators, the grain is shipped downriver. Much of it goes to New Orleans where it is loaded aboard ocean freighters for overseas destinations.

Petroleum products and coal rank second in overall tonnage shipped: gasoline, kerosene and fuel oil headed upriver from the oil fields of Texas and Louisiana. Large quantities of coal are also shipped upstream, mainly from the coal fields of central and southern Illinois and western Kentucky. Other products shipped on the river include fertilizers, sulfur, cement, sugar and dehydrated molasses.

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Revised: Saturday, October 13, 2001