Arlington County is an urban county of about 203,000 residents in the Commonwealth of Virginia, in the U.S., directly across the Potomac River from Washington, D.C. Originally part of the District of Columbia, the land now comprising the county was retroceded to Virginia in a July 9, 1846 act of Congress that took effect in 1847. At a land area of 26 square miles, it is geographically the smallest self-governing county in the United States. Arlington was ranked as the most educated city in 2006 by CNN Money. It is the location of Arlington National Cemetery and the Pentagon. Arlington apartments for rent comparison page shows most up to date rent information on Arlington apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.