The 15 jurisdictions of Virginia that are part of the federally designated Washington metropolitan area are generally thought of as Northern Virginia. But those include Warren, Clarke, and Spotsylvania counties as well as the city of Fredericksburg—places that culturally and politically belong more with the Old Dominion.
A more natural southern border would be the Rappahannock River, which forms the western border of Fauquier County and flows southeast to Fredericksburg. The river has long been the de facto dividing line between Northern Virginia and the rest of the state. Historian and author Tony Horwitz tells of driving south from Washington and reaching the first state visitors center—not at the Virginia border but at the Rappahannock.
“It’s a small but telling bit of symbolism: an internal border post, guarding the state’s heartland from the breakaway region of Northern Virginia. . . .” he wrote in State by State: A Panoramic Portrait of America. Most of Virginia above the Rappahannock River was occupied by Union troops during the Civil War, he noted, “and in the view of many state residents, it remains so today.”