The Missouri River drains one-sixth of the United States, encompassing over 529,350 square miles in all or portions of 10 states and Canada. The Missouri is the nations' longest river, flowing 2,341 miles through seven states from Three Forks, MT to join the Mississippi River near St. Louis, MO. Since the early 1800s, Congress has directed the U.S. Army Corps of Engineers to remove snags, stabilize river banks, construct and maintain navigation channels, build flood risk management structures (levees and dams), and provide hydroelectric power and recreational opportunities on the Missouri River. These activities provide benefits valued at nearly $2 billion per year. Some the these development activities on the Missouri River have come at the expense of the river's native fish and wildlife. The Corps is working to lessen these environmental impacts while maintaining the social and economic benefits of the system.