The Potomac River is the second largest source of freshwater for the Chesapeake Bay. This 384 mile long river's watershed covers over 15,000 square miles. Four states and Washington D.C. drain into the Potomac. Tributaries include the Anacostia, Shenandoah, Occoquan, and Monocacy Rivers. The Chesapeake Bay is the largest estuary in the United States, and boasts a watershed that covers over 64,000 square miles of land from New York to Virginia. Three rivers- the Susquehanna, the Potomac, and the James- provide 80 percent of the Bay's fresh water. Over sixteen million people live within the Bay's watershed.