Army Organization in the Defenses of Washington

The Defenses of Washington were organized into two distinct military divisions during the Civil War: the Defenses North of the Potomac River and the Defenses South of the Potomac River. Both divisions comprised the Department of Washington, reorganized as the Twenty-Second Army Corps on February 2, 1863. Each division comprised three brigades, a mixture of heavy artillery and infantry regiments. The troops supplementing these two sectors were organized into divisions named after their commanders. The department also comprised three military districts: the Distirct of Washington; District of Alexandria; and the District of St. Marys, all reporting to the commanding general of the corps. The District was organized to maintain military security within the confines of Washington City. The troops within the District of Alexandria, according to historian Frank J. Welcher, "served as city guards, and at the camps for convalescents, paroled prisoners, distribution, and drafted men," (F. Welcher, 1989). The District of St. Marys was added to the Department of Washington from the Department of Virginia and North Carolina in June 1864. The principal post of the district was the prisoner of war camp at Point Lookout on the tip of the peninsula in southern Marlyand.

For example, the Department of Washington, Twenty-Second Army Corps was comprised of these military organizations and units in April 1863:

• Defenses North of the Potomac (3 brigades)

• Defenses South of the Potomac (2 brigades)

• Abercrombie's Division (2 brigades) *Brigadier General John J. Abercrombie

• Casey's Division (3 brigades) *Major General Silas Casey

• Pennsylvania Reserves Division (3 brigades) *Colonel Horatio G. Sickel

• Cavalry Divsion (3 brigades) *Major General Julius Stahel

• Jewett's Independent Brigade [Corps of Observation] (5 infantry regiments and 1 artillery battery) *Colonel Albert B. Jewett

• District of Colombia (8 infantry regiments) *Brigadier General John H. Martindale

• District of Alexandria (4 infantry regiments and 1 artillery battery) *Brigadier General John P. Slough

• Artillery Defenses of Alexandria (2 heavy artillery regiments) *Brigadier General Robert O. Tyler

• Artillery Brigade South of the Potomac (5 heavy artillery regiments and battalions) *Colonel Williams Cogswell

• Light Artillery Camp [Camp Barry] (9 artillery batteries) *Brigadier General Albion P. Howe