Washington and Old Dominion Railroad

The Washington and Old Dominion Railroad (colloquially referred to as the W&OD) was an intrastate short-line railroad located in Northern Virginia. Its oldest line extended from Alexandria on the Potomac River northwest to Bluemont at the foot of the Blue Ridge Mountains near Snickers Gap, not far from the boundary line between Virginia and West Virginia. The railroad's route largely paralleled the routes of the Potomac River and the present Virginia State Route 7 (VA Route 7).

The line followed the winding course of Four Mile Run upstream from Alexandria through Arlington to Falls Church. At that point, the railroad was above the fall line and was able to follow a more direct northwesterly course in Virginia through Dunn Loring, Vienna, Sunset Hills (now in Reston), Herndon, Sterling, Ashburn, Leesburg, Paeonian Springs, Hamilton, Purcellville and Round Hill to its terminus at Bluemont, turning sharply to the west only after passing through Clarks Gap in Catoctin Mountain west of Leesburg. A branch connected the line to Rosslyn. The Washington & Old Dominion Railroad Trail (W&OD Trail), the Bluemont Junction Trail and several other trails have replaced much of the railroad's route.