Divisions of the United States Army

These eras represent the major evolutions of army division structure (there have been several minor changes during these times).

Many divisions overlap the years listed in the era categories, mainly due to the slow pace in which they were deactivated, inactivated, or otherwise disbanded.

Divisions in the United States Army have existed since the American Revolution, but during the 18th and 19th centuries, these were temporary organizations.

[1] The concept of the permanent United States Army division was formulated and put to the test following the turn of the 20th century.

In 1916, the permanent division would finally be authorized by Congress, resulting in a dramatic change in the Army's force structure.

George Washington organized the first divisions of the United States Army on 22 July 1775 in Boston, Massachusetts.

Arriving to take command of the Siege of Boston, he split the forces there into three divisions, each composed of two brigades of six to seven regiments.

[5] When the Army of the Potomac was first formed after the disastrous First Battle of Bull Run, the division was initially the largest unit.

[4] Administrative needs eventually led to the addition of a quartermaster, a commissary of subsistence, an ordnance officer, and a surgeon, all with the rank of major.

However, there were no enlisted personnel specifically assigned to support duties, instead requiring either line soldiers be detailed to carry them out or civilian workers employed.

The former removed the combat effectiveness of the units they were taken from, while the latter were more difficult to find and replace and tended to be less reliable and obedient.

The 76th through 91st and 94th through 104th Divisions existed primarily as officer billets with enlisted cadre; they were not completely reactivated until America's entry into World War II.

These non-divisional units numbered approximately 1.5 million soldiers, enough personnel to man roughly 100 more divisions.