Explanation : Washington, D.C., formally the District of Columbia and commonly referred to as Washington, “the District”, or simply D.C., is the capital of the United States. The Potomac River forms the District’s border with Virginia and has two major tributaries : the Anacostia River and Rock Creek. The highest natural elevation in the District is 409 feet (125 m) above sea level at Fort Reno Park in upper northwest Washington. The lowest point is sea level at the Potomac River. ....Read more