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The Potomac River (/pəˈtoʊmək/) drains the Mid-Atlantic United States, flowing from the Potomac Highlands into Chesapeake Bay. It is 405 miles (652 km) long, with a drainage area of 14,700 square miles (38,000 km2), and is the fourth-largest river along the East Coast of the United States and the 21st-largest in the United States. Over 5 million people live within its watershed.