The garrison consisted of a single company of Union soldiers who inspected traffic crossing the bridge and guarded it from potential saboteurs.

Part of the original ten-mile-square District of Columbia, the land now comprising the county was retroceded to Virginia in a July 9, 1846, act of Congress that took effect in 1847.

[6] The U.S. Army responded by creating the Department of Washington, which united all Union troops in the District of Columbia and Maryland under one command.

The forward march movement into Virginia, indicated in my despatches last night, took place at the precise time this morning that I named, but in much more imposing and powerful numbers.

The troops quartered at Georgetown, the Sixty-ninth, Fifth, Eighth and Twenty-eighth New York regiments, proceeded across what is known as the chain bridge, above the mouth of the Potomac Aqueduct, under the command of General McDowell.

Eight thousand infantry, two regular cavalry companies and two sections of Sherman's artillery battalion, consisting of two batteries, were in line this side of the Long Bridge at two o'clock.

Engineer officers under the command of then-Colonel John G. Barnard accompanied the army and began building fortifications and entrenchments along the banks of the Potomac River in order to defend the bridges that crossed it.

The two forts had largely been made redundant by the newer, stronger works atop the hills, and it was believed that neither played a crucial role any longer in the defenses of Washington.

These were eventually replaced, but the wide opening needed for the tracks proved to have a detrimental effect on the fort's defensive ability.

[20] Spurred in part by the Confederate attack on Fort Stevens north of Washington, several improvements were made, including the restoration of gates that had been removed when the railroad line was constructed.

[19] Gen. Christopher Columbus Augur, commander of the Department of Washington, recommended that Fort Jackson be assigned two light guns as armament during the reconstruction.

[21] After the surrender of General Robert E. Lee's Army of Northern Virginia on April 9, 1865, the primary reason for manned defenses protecting Washington ceased to exist.

Due to its rear-area nature and the fact that inspections were no longer needed to protect the Long Bridge against sabotage, Fort Jackson fell into the third-class category.

[22] The lumber used in the construction of Fort Jackson was either sold for salvage or scavenged by squatters, most of whom were freed slaves traveling north in a search for new lives following the ending of slavery in the United States.

Needy negro squatters, living around the forts, have built themselves shanties of the officers' quarters, pulled out the abatis for firewood, made cord wood or joists out of the log platforms for the guns, and sawed up the great flag-staffs into quilting poles or bedstead posts...

[24] A brickworks was also located nearby, sometimes utilizing the clay that formed the bastions of Fort Runyon as raw material for the bricks that would later go into the walls of Washington homes.

[26] Just south of the federal George Washington Memorial Parkway, between the CSX tracks and I-395, is Arlington County's Long Bridge Park.