Department (United States Army)

Department is an organizational term used by the U.S. Army, mostly prior to World War I, to describe named geographical districts created for control and administration of installations and units. In 1920, most of the named departments were redesignated as numbered Corps Areas. However, the Hawaiian, Panama Canal, and Philippine Departments retained their old names. In 1939, the Puerto Rican Department was created and in May 1941 the Panama Canal and Puerto Rican Departments were combined as the Caribbean Defense Command, although each was still referred to as a department.

The United States Army was divided into nine military districts by the War Department General Order, of March 19, 1813. They were increased to ten on July 2, 1814 but reduced to nine by consolidation of the 4th and 10th Military Districts in January 1815. Military districts were abolished, May 17, 1815.

At the end of the War of 1812, Military districts were superseded by ten Military Departments, divided equally between Divisions of the North and South, May 17, 1815.

Reorganization of the Army into Eastern and Western Departments, May 1821.

From 1837 to 1842, some of the Departments were subordinated to the Eastern and Western Divisions.

The Eastern and Western Divisions were restored, until 1853.

All departments were subordinated under one of three Divisions.

After October 31, 1853 the division echelon was eliminated and the six western departments consolidated into four (Departments of Texas, New Mexico, the West, and the Pacific), whose department commanders employed their troops as they saw fit. The system returned to six departments in 1858 when the Department of Utah was created in January, and the Department of the Pacific split into the Departments of California and Oregon in September.

During the American Civil War, a department was a geographical command within the Union's military organization, usually reporting directly to the War Department. Many of the Union's departments were named after rivers, such as the Department of the Potomac and the Department of the Tennessee. The geographical boundaries of such departments changed frequently, as did their names. As the armies became larger Departments began to be subordinated to Military Divisions, and the Departments were often sub divided into Districts and from 1862, Subdistricts. Much information on Civil War departments can be found in Eicher & Eicher, Civil War High Commands.

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