The U.S. Army was officially founded on 14 June 1775, when the Continental Congress authorized enlistment of riflemen to serve the United Colonies for one year. Each branch of the Army has a different branch insignia.

US Army Basic branches

• Infantry, 14 June 1775

Ten companies of riflemen were authorized by a resolution of the Continental Congress on 14 June 1775. However, the oldest Regular Army infantry regiment, the 3rd Infantry Regiment, was constituted on 3 June 1784, as the First American Regiment.

• Adjutant General's Corps, 16 June 1775

The post of Adjutant General was established 16 June 1775, and has been continuously in operation since that time. The Adjutant General's Department, by that name, was established by the act of 3 March 1812, and was redesignated the Adjutant General's Corps in 1950.

• Corps of Engineers, 16 June 1775

Continental Congress authority for a "Chief Engineer for the Army" dates from 16 June 1775. A corps of Engineers for the United States was authorized by the Congress on 11 March 1789. The Corps of Engineers as it is known today came into being on 16 March 1802, when the President was authorized to "organize and establish a Corps of Engineers … that the said Corps … shall be stationed at West Point in the State of New York and shall constitute a Military Academy." A Corps of Topographical Engineers, authorized on 4 July 1838, was merged with the Corps of Engineers on March 1863.

• Finance Corps, 16 June 1775

The Finance Corps is the successor to the old Pay Department, which was created in June 1775. The Finance Department was created by law on 1 July 1920. It became the Finance Corps in 1950.

• Quartermaster Corps, 16 June 1775

The Quartermaster Corps, originally designated the Quartermaster Department, was established on 16 June 1775. While numerous additions, deletions, and changes of function have occurred, its basic supply and service support functions have continued in existence.

• Field Artillery, 17 November 1775

The Continental Congress unanimously elected Henry Knox "Colonel of the Regiment of Artillery" on 17 November 1775. The regiment formally entered service on 1 January 1776.

• Armor, 12 June 1776

The Armor branch traces its origin to the Cavalry. A regiment of cavalry was authorized to be raised by the Continental Congress Resolve of 12 December 1776. Although mounted units were raised at various times after the Revolution, the first in continuous service was the United States Regiment of Dragoons, organized in 1833. The Tank Service was formed on 5 March 1918. The Armored Force was formed on 10 July 1940. Armor became a permanent branch of the Army in 1950.

• Ordnance Corps, 14 May 1812

The Ordnance Department was established by act of Congress on 14 May 1812. During the Revolutionary War, ordnance material was under supervision of the Board of War and Ordnance. Numerous shifts in duties and responsibilities have occurred in the Ordnance Corps since colonial times. It acquired its present designation in 1950. Ordnance soldiers and officers provide maintenance and ammunition support.

• Signal Corps, 21 June 1860

The Signal Corps was authorized as a separate branch of the Army by act of Congress on 3 March 1863. However, the Signal Corps dates its existence from 21 June 1860, when Congress authorized the appointment of one signal officer in the Army, and a War Department order carried the following assignment: "Signal Department--Assistant Surgeon Albert J. Myer to be Signal Officer, with the rank of Major, 27 June 1860], to fill an original vacancy."

• Chemical Corps, 28 June 1918

The Chemical Warfare Service was established on 28 June 1918, combining activities that until then had been dispersed among five separate agencies of Government. It was made a permanent branch of the Regular Army by the National Defense Act of 1920. In 1945, it was re-designated the Chemical Corps.

• Military Police Corps, 26 September 1941

A Provost Marshal General's Office and Corps of Military Police were established in 1941. Prior to that time, except during the Civil War and World War I, there was no regularly appointed Provost Marshal General or regularly constituted Military Police Corps, although a "Provost Marshal" can be found as early as January 1776, and a "Provost Corps" as early as 1778.

• Transportation Corps, 31 July 1942

The historical background of the Transportation Corps starts with World War I. Prior to that time, transportation operations were chiefly the responsibility of the Quartermaster General. The Transportation Corps, essentially in its present form, was organized on 31 July 1942. The Transportation Corps is headquartered at Fort Eustis, Virginia under the mantra "Spearhead of Logistics" and command of Brigadier General Brian R. Layer.

• Military Intelligence Corps, 1 July 1962

Intelligence has been an essential element of Army operations during war as well as during periods of peace. In the past, requirements were met by personnel from the Army Intelligence and Army Security Reserve branches, two-year obligated tour officers, one-tour levies on the various branches, and Regular Army officers in the specialization programs. To meet the Army's increased requirement for national and tactical intelligence, an Intelligence and Security Branch was established in the Army effective 1 July 1962, by General Order No. 38, on 3 July 1962. On 1 July 1967, the branch was re-designated as Military intelligence.

• Air Defense Artillery, 20 June 1968

The Air Defense Artillery separated from the Field Artillery and was established as a basic branch on 20 June 1968, per General Order 25, 14 June 1968.

• Aviation, 12 April 1983

Following the establishment of the U.S. Air Force as a separate service in 1947, the Army began to develop further its own aviation assets (light planes and rotary wing aircraft) in support of ground operations. The Korean War gave this drive impetus, and the war in Vietnam saw its fruition, as Army aviation units performed a variety of missions, including reconnaissance, transport, and fire support. After the war in Vietnam, the role of armed helicopters as tank destroyers received new emphasis. In recognition of the growing importance of aviation in Army doctrine and operations, Aviation became a separate branch on 12 April 1983.

• Special Forces, 9 April 1987

The first Special Forces unit in the Army was formed on 11 June 1952, when the 10th Special Forces Group was activated at Fort Brag, North Carolina. A major expansion of Special Forces occurred during the 1960s, with a total of eighteen groups organized in the Regular Army, Army Reserve, and Army National Guard. As a result of renewed emphasis on special operations in the 1980s, the Special Forces Branch was established as a basic branch of the Army effective 9 April 1987, by General Order No. 35, 19 June 1987. Special Forces are part of U.S. Special Operations Forces

• Civil Affairs Corps, 16 October 2006

The Civil Affairs/Military Government Branch in the Army Reserve Branch was established as a special branch on 17 August 1955. Subsequently redesignated the Civil Affairs Branch on 2 October 1955, it has continued its mission to provide guidance to commanders in a broad spectrum of activities ranging from host-guest relationships to the assumption of executive, legislative, and judicial processes in occupied or liberated areas. Became a basic branch effective 16 October 2006 per General Order 29, on 12 January 2007.

• Psychological Operations, 16 October 2006

Established as a basic branch effective 16 October 2006 per General Order 30, 12 January 2007. Name will change to Military Information Support Operations at a date TBD.

• Logistics, 1 January 2008

Established by General Order 6, 27 November 2007. Consists of multi-functional logistics officers in the rank of captain and above, drawn from the Ordnance, Quartermaster and Transportation Corps.

US Army Special branches

• Army Medical Department, 27 July 1775

The Army Medical Department and the Medical Corps trace their origins to 27 July 1775, when the Continental Congress established the Army hospital headed by a "Director General and Chief Physician." Congress provided a medical organization of the Army only in time of war or emergency until 1818, which marked the inception of a permanent and continuous Medical Department. The Army Organization Act of 1950 renamed the Medical Department as the Army Medical Service. In June 1968, the Army Medical Service was re-designated the Army Medical Department. The Medical Department has the following branches:

• Medical Corps, 27 July 1775
• Army Nurse Corps, 2 February 1901
• Dental Corps, 3 March 1911
• Veterinary Corps, 3 June 1916
• Medical Service Corps, 30 June 1917
• Army Medical Specialist Corps, 16 April 1947

• Chaplain Corps, 29 July 1775

The legal origin of the Chaplain Corps is found in a resolution of the Continental Congress, adopted 29 July 1775, which made provision for the pay of chaplains. The Office of the Chief of Chaplains was created by the National Defense Act of 1920.

• Judge Advocate General's Corps, 29 July 1775

The Office of Judge Advocate of the Army may be deemed to have been created on 29 July 1775, and has generally paralleled the origin and development of the American system of military justice. The Judge Advocate General Department, by that name, was established in 1884. Its present designation as a corps was enacted in 1948.