In the opening days of the American Civil War, the defenses of Washington D.C. were primarily concerned with an overland attack on the capital city of the United States.

[1] Fort Washington's vulnerability was highlighted in the 1862 clash of the USS Monitor and the CSS Virginia, two wholly ironclad ships.

They were also concerned with the potential intervention of European nations on the side of the Confederacy, possibly adding a major naval threat to the city.

Foreign intervention would bring against us always in superior naval force on the Potomac, and we are, even now, threatened with Confederate iron-clads fitted in English Ports.

...and by constructing a battery of ten guns and a covering work on the opposite shore of the Potomac, at [or] near Roziers Bluff [the situation can be remedied].

[3]Then-colonel John Gross Barnard, the chief military engineer for the defenses of Washington, went to work on the commission's recommendation with haste.

Rosiers Bluff, a 100-foot (30 m) high Maryland cliff six miles (10 km) south of the city, and pointed out in the commission's report was found to be an excellent site for the new fort.

[2] The layout would largely follow the plans laid out in West Point instructor Dennis Mahan's A Treatise on Field Fortification, which said As a field fort must rely entirely on its own strength, it should be constructed with such care that the enemy will be forced to abandon an attempt to storm it, and be obliged to resort to the method of regular approaches used in the attack of permanent works.

To effect this, all the ground around the fort, within range of the cannon, should offer no shelter to the enemy from its fire; the ditches should be flanked throughout; and the relief be so great as to preclude any attempt at scaling the work.

Due to its location along the coast, the use of iron in the fortifications was limited, and most of the fort was constructed of earth and locally cut lumber.

On August 20, 1863, Seward, President Abraham Lincoln, Secretary of War Edwin Stanton, and the recently promoted General Barnard visited the new construction.

After spending several months recuperating in New York City, Foote was named commander of the South Atlantic Blockading Squadron.

Sunday afternoons were a soldier's free time, and this was usually filled by writing letters home, bathing, or simply catching up on extra sleep.

The nearest land route, Piscataway Road, was over a mile away and was used only when the Potomac froze over and ended water traffic.

Ordinary soldiers were rarely granted a furlough to Alexandria, which lay just across the river, or to Washington, six miles (10 km) distant.

On one scheduled occasion, the Sewards attended a training drill at which the fort's gunners were to use a target anchored in the middle of the Potomac, two miles (3 km) away.

The embarrassed Union gunners were forced to fire on alternative targets while Mrs. Seward conducted an impromptu lunch in one of the fort's bunkers.

With the end of the war, the federal government began turning over Washington's forts and the land on which they rested to their pre-war owners.

With the coming of peace, commercial traffic had returned to the Potomac, and firing 400-pound cannonballs over the heads of steamer captains was frowned upon for safety reasons.

Planners wrote, "emphasis will be placed on the every- day camp life of the patriot man-at-arms, on the long and patient labor, the sacrifice, and the self-reliance demanded in the struggle to bring forth the first modern republic."

The park was to include the encampment, a parade ground and a primitive fort made of wood and staffed by period reenactors.