The Potomac River is located on the east coast of the United States, and runs through Maryland, Virginia, West Virginia, and Washington, D.C. before it empties into the Chesapeake Bay. It is over 380 miles long and wider than 11 miles at its widest point.[1]
"The Swamp" as a pejorative nickname for bureaucrats who fill federal government buildings there is based on the formerly mosquito-infested climate there associated with the Potomac River.
The Potomac River had enormous strategic importance during the Civil War, and was central to the Battle of Antietam in 1862.