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).The Department of the Navy is headed by the secretary of the Navy, also known as the SECNAV in naval jargon, who has the authority to conduct all of the affairs of the department, subject to lawful authority, the secretary of defense, and the president.They supervise their respective military services of the Department of the Navy, and in a separate capacity serve as members of the Joint Chiefs of Staff.Former famous marines have also voiced support including Lieutenant Colonel Oliver North and Gunnery Sergeant R. Lee Ermey, who stated in 2010 "When we die, when mama and dada get that letter of condolence, it would be kind of nice if the Marine Corps was mentioned...just change the letterhead."[8] Former secretaries of the Navy Paul Nitze and John Howard Dalton have also supported the change.
Navy Department, mainly the Office of the Secretary, organizational structure (2006)