An Act to establish the Executive Department to be denominated the Department of War, June 27, 1789, with Senate annotations
The Department of War, established in 1789, oversaw all military affairs until Congress created a separate Navy Department in 1798. The National Security Act, passed by Congress in 1947, designated departments for the Army, Navy, and the Air Force. A National Military Establishment, renamed the Department of Defense in 1949, administered these departments.
Records of the U.S. Senate, National Archives and Records Administration, Washington, D.C.
Creating a Department of War
When the First Congress met in 1789, one of the primary orders of business was the creation of new executive departments to aid the president. Congress promptly established three such departments: the Department of Foreign Affairs (now the Department of State), the Department of Treasury, and the Department of War (now the Department of Defense), which was charged with administering the Army. To strengthen national defense, the First Congress augmented state and volunteer militias with a standing national army.