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At the end of the War of 1812, Military districts were superseded by ten Military Departments, divided equally between Divisions of the North and South, May 17, 1815.
Division of the North, May 17, 1815 – May 18211st Military Department, 1815–172nd Military Department, 1815–183rd Military Department, 1815–17Consolidated 1st and 3rd Military Departments, 1817–19Consolidated 1st and 3rd Military Departments, 1818–214th Military Department, 1815–19Consolidated 1st, 3rd, and 4th Military Departments, 1819–215th Military Department, 1815–21.Division of the South, May 17, 1815 – May 18216th Military Department, 1815–18217th Military Department, 1815–18218th Military Department, 1815–19, 1820–219th Military Department, June 1819 – June 182110th Military Department, 1815–1821Reorganization of the Army into Eastern and Western Departments, May 1821.
Eastern Department, 1821–37Western Department, 1821–37Right Wing, Western Department, 1832–37Army of the Frontier, 18321st Army Corps, North West Army, 1832Army of the Southwestern Frontier, 1834–37From 1837 to 1842, some of the Departments were subordinated to the Eastern and Western Divisions.
Eastern Division, 1837–427th Military Department, 1837–41Western Division, 1837–421st Military Department, 1837–422nd Military Department, 1837–427th Military Department, 1841–421st Military Department, 18432nd Military Department, 1843–513rd Military Department, 1842–484th Military Department, 1842–535th Military Department, 1842–528th Military Department, 1842–469th Military Department, 1842–45 (Florida)The Eastern and Western Divisions were restored, until 1853.
Eastern Division, 1844–485th Military Department, 1844–488th Military Department, 1844–46Western Division, 1844–482nd Military Department, 1844–483rd Military Departments, 1844–484th Military Department, 1842–539th Military Department, 184510th Military Department, 1846–1853 (California and Oregon to 1848)All departments were subordinated under one of three Divisions.
Eastern Division, 1848–531st Military Department, 1848–53; consolidated 1st and 3d Military Departments, 1849–502nd Military Department, 1848–51; consolidated 1st and 2d Military Departments, 1848–493rd Military Departments, 1848, 1850–534th Military Departments, 1848–53; consolidated 3d and 4th Military Departments, 1848Western Division, 1848–53consolidated 5th and 6th Military Departments, 18485th Military Department, 1848–526th Military Department, 1848–537th Military Department, 1848–538th Military Department, 1848–49, 1851–539th Military Department, 1849–53 (New Mexico)Pacific Division, 1848–53,(California and Oregon)10th Military Department, 1846–1853 (California and Oregon to 1848)11th Military Department, 1848–1853 (Oregon)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.
Department of the East, 1853 – August 17, 1861Department of the West, 1853 – July 3, 1861Department of Texas, 1853 – April 22, 1861Department of the Pacific, 1853-September 13, 1858; January 15, 1861 – June 27, 1865Department of New Mexico, 1853 – June 27, 1865Department of Utah, June 30, 1857 – July 3, 1861Department of the Platte, April 4, 1858 – May 16, 1859Department of California, September 13, 1858 – January 15, 1861Department of Oregon, September 13, 1858 – January 15, 1861During 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.
Union Army Divisions, Departments and DistrictsMilitary Division of the Atlantic, 1865–66Department of the East, 1865–73; independent 1866–68Middle Military Department, 1866Department of North Carolina, 1865–66; to Department of the CarolinasDepartment of South Carolina, 1865–66; to Department of the CarolinasDepartment of the Carolinas, May, 1866; renamed Department of the South, June 1866; to Second Military DistrictDepartment of Virginia, 1865–66; to First Military DistrictMilitary Division of the Tennessee, 1865–67Department of Alabama, 1865–66Department of Georgia, 1865–66Department of the South, 1866; to Third Military DistrictDepartment of Kentucky, 1865–66Department of Mississippi, 1865–66; to Fourth Military DistrictDepartment of Tennessee, 1865–66Department of the Cumberland, 1866District of Tennessee, 1866Sub-district of Tennessee, 1866Military Division of the Missouri, 1865; to Military Division of the MissouriDepartment of Arkansas, 1865; to Military Division of the GulfDepartment of the Missouri, 1865; to Military Division of the MississippiDepartment of the Northwest, 1865; merged into Department of the MissouriMilitary Division of the Mississippi, 1865–66Department of the Ohio, 1865–66Department of Arkansas, 1865–66; to Military Division of the MissouriDepartment of the Missouri, 1865–66; to Military Division of the MissouriDepartment of the Platte, 1866; to Military Division of the MissouriMilitary Division of the Gulf, 1865–66Department of Arkansas, 1865; to Military Division of the MississippiDepartment of Louisiana, 1865–66; to Fifth Military DistrictDepartment of Texas, 1865–66; to Fifth Military DistrictDepartment of Florida, 1865–66; to Third Military DistrictDepartment of Mississippi, 1865; to Military Division of the TennesseeMilitary Division of the Pacific, 1865–68, Division of the Pacific 1869–91Department of the Columbia, 1865–1913Department of California, 1865–1913Military District of Alaska, October 18, 1867 – March 18, 1868Department of Alaska, March 18, 1868 – July 1, 1870; merged into Department of the ColumbiaMilitary Division of the Missouri, 1866–91Department of Arkansas, 1866–67; to Fourth Military DistrictDepartment of Dakota, 1866–91Department of the Missouri, 1866–91Department of the Platte, 1866–91Department of Texas, 1871–80First Military District, 1867–70 (Virginia)Second Military District, 1867–68 (North Carolina and South Carolina)Third Military District, 1867–68 (Georgia, Alabama and Florida)Fourth Military District, 1867–70 (Arkansas and Mississippi)Fifth Military District, 1866–70 (Texas and Louisiana)Military District of Georgia, 1870–71Division of the Atlantic, 1868–91Department of the East, 1868–73Department of the Lakes, 1868–73Department of Washington, 1868–691st Military District, 1869–70 (Virginia)Department of Virginia, 1870Department of the South, 1876–83Department of the Gulf, 1877–78Department of the East, 1877–91Division of the South, 1869–76Department of the Cumberland, 1869–70Department of the Gulf, 1871–75Department of Louisiana, 1869–70Department of the South, 1869–76Department of Texas, 1870–714th Military District, 1869–70 (Arkansas and Mississippi)District of Baton Rouge, 18761st Subdistrict of Georgia, 1870–71Division of the Pacific, 1869–91Department of Alaska, 1869–70District of Arizona, 1869–70District of the Humboldt, 1869Sub-district of Southern Arizona, 1869–70Department of Arizona, 1870–91Department of California, 1870–91Department of the Columbia, 1870–91Department of the South, 1876–83Fort Johnson, NC, 1876–81Military Division of the Gulf, 1881Department of Arkansas, 1881Department of Texas, 1881Department of Texas, 1882–1904Department of the East, 1891–1904Department of the Platte, 1891–98Department of the Missouri, 1891–1904Department of Dakota, 1891–1904Department of Arizona, 1891–1893Department of California, 1891–1904Department of the Columbia, 1891–1904Department of Colorado, 1893–1904Department of Alaska, 1900–01Department of the Lakes, 1898–1913Department of the Gulf, 1898–99Department of California, 1898Military District of Hawaii, Sept. 22 – Nov. 7, 1898Department of the Pacific and 8th Army Corps, 1898 – March 20, 1900Division of the Philippines, March 20, 1900 – 1911Northern Luzon, 1900–02Department of Southern Luzon, 1900–01Department of Visayas, 1900–11Department of Mindanao and Jolo, 1900–14Department of North Philippines, 1901–02Department of South Philippines, 1901–02Department of Luzon, 1902–14The Army Departments were reorganized under new Divisions until 1907, when the Division echelon was disbanded.
Atlantic Division, 1903–07Department of the East, 1903–13Department of the Gulf, 1904–13Northern Division, 1904–07Department of Dakota, 1904–11Department of the Lakes, 1904–11Department of the Missouri, 1904–07Southwestern Division, 1904–07Department of Colorado, 1904-11Department of Texas, 1904–13Pacific Division, 1904–07Department of California, 1904–13District of Hawaii, 1910–1911Department of the Columbia, 1904–13The Departments where again organized under new Divisions.
Eastern Division, 1911–13Department of the East, 1911–13Department of the Gulf, 1911–13Central Division, 1911–13Department of the Lakes, 1911–13Department of the Missouri, 1911–13Department of Texas, 1911–13Western Division, 1911–13Department of California, 1911–13Department of the Columbia, 1911–13District of Hawaii, 1911–13Philippines Division, 1911–1913Department of Mindanao and Jolo, 1911–14Department of Luzon, 1911–14Eastern Department, 1913–1920Southern Department, 1913–1920Central Department, 1913–1920Western Department, 1913–1920Hawaiian Department, 1913–1920Philippine Department, 1913–1942Department of Mindanao and Jolo, 1913–14Department of Luzon, 1913–14North Atlantic, South Atlantic, and Pacific Coast Artillery DistrictsNortheastern DepartmentNortheastern Coast Artillery DistrictEastern DepartmentEastern Coast Artillery DistrictSoutheastern DepartmentSoutheastern Coast Artillery DistrictSouthern DepartmentSouthern Coast Artillery DistrictCentral DepartmentWestern DepartmentWestern Coast Artillery DistrictHawaiian DepartmentPhilippine DepartmentPanama Canal Department, June 26, 1917 – 1920Panama Coast Artillery District, June 26, 1917 – 1920