Up until the mid-1630s, each town had its own militia company (also known as "trained bands") which was commanded by an officer with the rank of captain. After December 13, 1636, this changed. That day that the Massachusetts militia was organized into the North, South, and East Regiments. Today's 181st Infantry Regiment, 101st Field Artillery Regiment, and 101st Engineer Battalion (United States) respectively trace their origins to these three regiments. The militia companies were nominally under the command of the colonial governor, but, in practice, operated as independent units. The regimental organization did much to improve the organization and leadership of the militia. Three years later the Hampshire Regiment was raised in Springfield, MA; today's 104th Infantry Regiment traces its origins to that unit.
