Although the Virginia militia was organized officially by Governor Thomas Dale in 1611, in reality the colonists had been organized for their mutual defense against hostile Indians and Europeans since establishing Jamestown in 1607. As the colony grew and counties were formed, the House of Burgesses refined the organization of the militia, which was under the authority of the governor. By the time the revolutionary war began, the militia had been structured along English lines, with regiments in each county commanded by a county lieutenant holding the rank of colonel.

To ensure "conformity in their exercise and evolutions, so that when the different battalions join in brigades there may be no mistake or confusion," the third revolutionary convention passed an ordinance at its session begun on July 17, 1775, establishing the Office of the Adjutant General. Both the office and the trend toward uniformity continued after the war. The Civil War marked the end of the militia system of 250 years.