Free
Flowing over rapids and falls, the Mississippi River drops nearly 700 feet between its headwaters at Lake Itasca and the Twin Cities (Minneapolis and Saint Paul).
It keeps dropping until it reaches the Gulf of Mexico. The river also gets broader as it flows south. Its water level continually changes, too. All these changes make it difficult to keep the river safe for navigation and its shores safe for habitation. But over the years, engineers have devised dams, levees, and locks to control the mighty Mississippi.
