Fort Corcoran, Arlington Line, Virginia

Federal soldiers posing near Fort Corcoran's sallyport (rear entrance).

Fort Corcoran was one of the first forts constructed as part of the Defenses of Washington in May-June 1861.

It formed part of a section of earthworks that protected Aqueduct Bridge and Long Bridge along the Potomac.

General John G. Barnard describes the defense as such:
To that portion of the defenses covering the Aqueduct and Long Bridges and the intermediate heights of Arlington, the above term was quite commonly applied, not only from its importance, but from the fact that, as elsewhere explained, the system had its beginning in some of these works, and that, under the pressure of danger after the battle of Bull Run, the first approach to a connected line was made by interpolating the lunettes with stockaded gorges, Forts Woodbury, Cass, Tillinghast, and Craig, between Forts Corcoran and Albany.
Fort Corcoran was named in honor of Colonel Michael Corcoran, commanding 69th New York Infantry, who constructed the fort.