Arlington County is an urban county of about 206,800 residents in the Commonwealth of Virginia. It is located directly across the Potomac River to the west of Washington, D.C. Formerly part of the District of Columbia, the land now composing the county was retroceded to Virginia on July 9, 1846, in an act of Congress that took effect in 1847. Despite being organized politically as a "county" in Virginia, it is considered a Central City of the Washington Metropolitan Area by the Census Bureau, along with the adjacent cities of Washington and Alexandria, Virginia. At a land area of 26 sqmi, it is geographically the smallest self-governing county in the United States. In 2005 Arlington was ranked first among walkable cities in the United States by the American Podiatric Medical Association. CNN Money ranked Arlington as the most educated city in 2006 with 35.7% of residents having held graduate degrees. In October 2008, BusinessWeek ranked Arlington as the safest city in which to weather a recession, with a 49.4% share of jobs in 'strong industries'. Along with five other Northern Virginia counties, Arlington ranked among the twenty U.S. counties with the highest median household income in 2006. Arlington is the location of Arlington National Cemetery, National Airport, the Pentagon, the USMC War Memorial, the US Air Force Memorial, and numerous other monuments. (via Wikipedia)