Washington County, D.C.

The County of Washington was one of five original political entities within the District of Columbia, the capital of the United States. Formed by the Organic Act of 1801 from parts of Montgomery and Prince George's County, Maryland, Washington County referred to all parts of the District of Columbia "on the east side of the Potomac, together with the islands therein." The bed of the Potomac River was considered to be part of Washington County as well.Alexandria County, containing the City of Alexandria formed the portion of the District ceded by the state of Virginia. It was returned to Virginia by Congress in 1846, thereby making Washington County and the District of Columbia coterminous. At times, however, the term "Washington County" was used to refer to only the remainder of the District that was part of neither Georgetown nor Washington City.

Starting in 1801, Washington County was governed by a board of commissioners, or a levy court, made up all of the Justices of the Peace, or magistrates, of the county appointed by the President and the number of those were not fixed. In 1812, the board was reorganized with seven magistrates, two from east of Rock Creek but outside of Washington City, two from west of Rock Creek but outside of Georgetown and three from Georgetown, with none from Washington City until 1848 when four members from the City were added. The board was again changed 1863 when it was reduced to nine members, three from the city of Washington, one from Georgetown, and five from county lands outside the city. These justices carried out the duties of county commissioners. Despite being within the federal territory, Congress left Washington County subject to the laws of Maryland.

Washington County included Pleasant Plains, the estate of the Holmead family; Edgewood, home of Treasury Secretary Salmon P. Chase; and Petworth, the estate of Colonel John Tayloe III. Also contained in Washington County was the U.S. Soldiers' Retirement Home, where President Abraham Lincoln lived during his summers as President. Despite its comparatively large geographic size, Washington County was sparsely populated until the end of the 19th century.

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