Arlington, Virginia Originally part of the area surveyed for the nation’s capital, the portion on the west bank of the Potomac River was returned to the Commonwealth of Virginia by the U.S. Congress in 1846. This area was known as Alexandria City and Alexandria County until 1920 when the county portion was renamed Arlington County. An urban county of about 26 square miles located directly across the Potomac River from Washington DC. Arlington’s central location in the Washington DC metropolitan area, its ease of access by car and public transportation, and its highly skilled labor force have attracted an increasingly varied residential and commercial mix. In 2000, Arlington was the 13th most densely-population jurisdiction in the U.S. (7,287 persons per square mile.) As of January 1, 2011, the population density was 8,150 per square mile. Click on postcard for direct website links; & to obtain more information about Arlington, Virginia USA & surrounding area vacation attractions .