During the Civil War, the U.S. Army constructed an elaborate system of fortifications to protect the capital. By war's end, Washington D.C. was one of the most heavily fortified cities in the world.
General Barnard declared that the general profiles, or sections, of the works were derived from those in Dennis Hart Mahan's A Treatise on Field Fortifications. Mahan, professor at the United States Military Academy at West Point, 1824-1871, was revered by multiple generations of future career army officers, including Barnard and Major General George B. McClellan. Generally, the Army Engineers planned the forts for approximately a 500-man garrison and for about 16 guns. "In the construction of these works the heights of the interior crest of the parapet was from 7 to 9 feet above the parade; the thickness of the parapet ranged from 12 to 18 feet; the ditches were usually 6 feet deep, and a few feet beyond the counterscarp a glacis was constructed upon which an abattis was placed; revetments of plank, vertical posts, fascines or sod were used, the cheeks of embrasures being revetted with gabions."
An Army Engineer publication on "The Art of Fortification," described the forts this way:
The Army Engineers also constructed numerous batteries between the forts. Major General George B. McClellan wrote: " The intermediate points [between the forts] were occupied by lunettes, redoubts, batteries, etc., and in a few cases these were united by infantry parapets. The entire circumference of the city was thus protected. " The Commission that studied the fortifications in late 1862, after examining and reporting on each fortification, recommended the construction of "numerous batteries . . . in the intervals between the forts." By constructing these batteries, the intervening space between the forts was also covered by artillery fire. Not all the batteries received guns; various authors report that over ninety batteries were not armed.
In his post-war report, published in 1871, Barnard described the batteries:
During the Civil War, the U.S. Army erected numerous wooden blockhouses to protect railroad lines, bridges, roads, and important defiles. Likewise, the Army erected blockhouses in the defenses of Washington, D.C. The Army designated three of these blockhouses by numbers: Blockhouse No. 1 and Blockhouse No. 2 were located near Hunting Creek Valley, one at the north side of the valley at the Little River Turnpike and one on Telegraph Road near the bridge over Hunting Creek, and Blockhouse No. 3 on the Leesburg Turnpike near Fort Ward.
The Trenches and Rifle Pits
The Defenses of Washington, the main forts, were fully connected by earthen trenches and rifle pits. According to General Barnard, "In addition to the forts proper, there were between the forts [and batteries], and forming as it were the curtains, some 20 miles [approximately 35,711 yards] of rifle trenches . . ."The whole line was connected by rifle-trenches which were in fact lines of infantry parapet, furnishing emplacement for two ranks of men and affording covered communication along the line . . ."
Barnard described the trenches in detail:
The Water Defense
Both Fort Foote (Fort Washington, Maryland) and Battery Rodgers (Jones Point Park in Alexandria, Virginia) anchored the defenses on the Potomac Rivers' southern approach and were often referred to as water or river or shore batteries. No enemy forces attempted to ascend the river for an attack on Washington so it is difficult to assess the value of these fortifications. At the end of the war, the Army had numerous proposals for the post-war use of the fort and battery. The Army did not retain Battery Rodgers but it did keep Fort Foote, which in association with Fort Washington was to repel invasions and raids up the river. The Army Engineers remodeled and enlarged Fort Foote during its use but stopped using it as a water defense in 1874. The site was abandoned in 1877, but was reactivated for a short period during the Spanish American War.
Additionally, the Army Engineers constructed obstructions that could be moored in the Potomac River, near Fort Foote, and "render the shore batteries [Fort Foote and Battery Rodgers] more efficient for the protection of Washington against maritime attack." In July 1864, Congress appropriated $300,000.00 for the fabrication of the obstructions and Lt. Colonel Barton S. Alexander, who succeeded General Barnard as Chief Engineer,, designed "a series of floats holding up a 400-foot-long chain with 23 anchors . . ." that some referred to as the "Alexandria Chain," but they were unused during the war. After the war, the Army held on to the obstructions and, in 1868, offered them to the Secretary of the Navy who, it turned out, considered them worthless. The obstructions remained stored in a shed near Fort Foote, deteriorating, at least into the early 1870s.
To facilitate the movement of men and supplies, the Union army constructed a system of military roads that encircled city.
In his 1871 report on the defenses of Washington, Barnard described the roads as such:
Almost as important as the roads for movement of supplies, equipment and materiel were the bridges. The only three bridges across the Potomac were Long Bridge, Aqueduct Bridge and Chain Bridge until 1864 when a railroad bridge was added, next to Long Bridge. The Navy Yard Bridge and Benning's Bridge crossed the Anacostia River, or as some called it the Eastern Branch. Fortifications and a guard unit protected all of these bridges. In addition, bridges on various roads crossed lesser streams and creeks. All the bridges required maintenance and in most instances, improvements. Without the bridges, the roads would not have been of much use.
Last updated: August 27, 2020