The United States Navy was founded on October 13, 1775, when Congress enacted the first legislation creating the Continental Navy of the American Revolution. The Department of the Navy and the Office of Secretary of the Navy were established by act of April 30, 1798 (10 U.S.C. 5011, 5031). For 9 years prior to that date, by act of August 7, 1789 (1 Stat. 49), the Secretary of War oversaw the conduct of naval affairs.
The National Security Act Amendments of 1949 provided that the Department of the Navy be a military department within the Department of Defense (63 Stat. 578).
Department of the Navy in the United States Government Manual