The history of the U.S. Armed Forces dates to 14 June 1775, with the creation of the Continental Army, even before the Declaration of Independence marked the establishment of the United States. The Continental Navy, established on 13 October 1775, and Continental Marines, established on 10 November 1775, were created in close succession by the Second Continental Congress in order to defend the new nation against the British Empire in the American Revolutionary War.

These forces demobilized in 1784 after the Treaty of Paris ended the War for Independence. The Congress of the Confederation created the current United States Army on 3 June 1784. The United States Congress created the current United States Navy on 27 March 1794 and the current United States Marine Corps on 11 July 1798. All three services trace their origins to their respective Continental predecessors. The 1787 adoption of the Constitution gave the Congress the power to "raise and support armies", to "provide and maintain a navy" and to "make rules for the government and regulation of the land and naval forces", as well as the power to declare war. The president is the U.S. Armed Forces' commander-in-chief.

The United States Coast Guard traces its origin to the founding of the Revenue Cutter Service on 4 August 1790 which merged with the United States Life-Saving Service on 28 January 1915 to establish the Coast Guard. The United States Air Force was established as an independent service on 18 September 1947; it traces its origin to the formation of the Aeronautical Division, U.S. Signal Corps, which was formed 1 August 1907 and was part of the Army Air Forces before becoming an independent service as per the National Security Act of 1947. The United States Public Health Service Commissioned Corps was formerly considered to be a branch of the United States Armed Forces from 29 July 1945 until its status as such was revoked on 3 July 1952.[21]

The United States Space Force was established as an independent service on 20 December 2019. It is the sixth branch of the U.S. military and the first new branch since the establishment of the independent U.S. Air Force in 1947.[22] It traces its origin to the formation of the Air Force Space Command, which was formed 1 September 1982 and was a major command of the United States Air Force.