The 100-foot wide Washington and Old Dominion Railroad Regional Park (W&OD) is one of the skinniest parks in the commonwealth of Virginia, but also one of the longest - 45 miles in length. The W&OD takes its name from the railroad whose trains ran along the right-of-way from 1859 until 1968. The entrepreneurs who founded the rail line dreamed of bringing coal and other riches from the Appalachians to the Port of Alexandria, but those dreams were never fully realized. Less than a decade after it was built, the railroad was almost destroyed during the Civil War.

After the war, the railroad was slowly rebuilt and then saw a series of changes of ownership and objectives. The heyday of the W&OD came early in the 20th Century, when it provided service three times daily from Alexandria to Falls Church, Leesburg and Purcellville, with stops at such hamlets as Dunn Loring, Hunter Station and Paeonian Springs.

When the W&OD ceased operations in 1968, the Virginia Electric and Power Company (VEPCO, now Virginia Power) bought the right-of-way for its electric power transmission lines. The Northern Virginia Regional Park Authority tried for years to acquire the use of the railroad right-of-way. Agreement was finally reached in 1977 for NVRPA to purchase the right-of-way in stages. The purchase was completed in 1982.

The first segment of the W&OD Trail was opened in 1974 within the City of Falls Church. This portion was built as the result of a special agreement with VEPCO under which the Regional Park Authority was allowed to judge whether a trail of this sort would prove to be popular. It did, and so, after the property was purchased, the trail was built in sections until its completion to Purcellville in 1988. Trail users today may enjoy 45 miles of asphalt trail and 32.5 miles of crushed stone and dirt bridle paths. In 1987, the W&OD was designated a National Recreation Trail by the U.S. Department of the Interior.