Northern Virginia comprises several counties and independent cities in the Commonwealth of Virginia, in a widespread region generally radiating southerly and westward from Washington, D.C. With 2.8 million residents (about a third of the state), it is the most populous region of Virginia and the Washington metropolitan area. As the term is most often used, it excludes such areas as Warren County and Winchester; "Northeastern Virginia" more closely approximates the area usually meant.
Communities in the region form the Virginia portion of the Washington Metropolitan Area and the larger Baltimore-Washington Metropolitan Area. Northern Virginia is the highest-income region of Virginia, having seven of the 20 highest-income counties in the nation, including the three highest as of 2009.
Northern Virginia's transportation infrastructure includes major airports Ronald Reagan Washington National Airport and Dulles International, several lines of the Washington Metro subway system, the Virginia Railway Express suburban commuter rail system, transit bus services, bicycle lanes and trails, and an extensive network of Interstate highways and expressways.
Notable features of the region include the Pentagon and the Central Intelligence Agency, and the many companies which serve them and the federal government. The area's attractions include various monuments and Colonial and Civil War-era sites such as Mount Vernon and Arlington National Cemetery. It is the most affluent region in the nation.