Naval Arm of the United States Military
The United States Department of the Navy (DoN) is one of the three military departments within the Department of Defense of the United States of America. It was established by an Act of Congress on 30 April 1798, at the urging of Secretary of War James McHenry, to provide a government organizational structure to the United States Navy (USN); since 1834, it has exercised jurisdiction over the U.S. Marine Corps (USMC) and, during wartime, the U.S. Coast Guard (USCG), though each remains an independent service branch. It is led by the Secretary of the Navy (SECNAV), a statutory civilian officer.
Department of the Navy was an executive department, whose secretary served on the president's cabinet, until 1949, when amendments to the National Security Act of 1947 established the Department of Defense as a unified department for all military services; the DoN, along with the Department of the Army and Department of the Air Force, became a component of the DoD subject to the authority, direction and control of the Secretary of Defense.
From 2001 to 2019, proposals to rename the Department of the Navy to the Department of the Navy and Marine Corps were introduced with wide support in the United States Congress, but failed due to the opposition of Senator and former U.S. Navy officer John McCain.