Detachment Alpha was activated on 15 August 1976 at Marine Corps Air Station Cherry Point, NC. Detachment Alpha fell under the Second Force Service Support Group which was one of the largest of two detachments that were implemented under the combat service support concept to serve as a direct support for units of the Second Marine Aircraft Wing located at Cherry Point, NC and Beaufort, SC.
The command was originally tasked to provide specialized support to the Marine Corps Air Station, Cherry Point and the 2nd Marine Aircraft Wing. Additionally the command provides personnel via the Fleet Assistance Program in the fields of freight and passenger transportation, disbursing, postal and exchange services.
On 10 August 1987 the detachment was officially re-designated to Combat Service Support Detachment 21, the combat ready nucleus of 2nd MAWs contingency CSS element.
In April 1988, the detachment gained the additional mission of the Arrival/Departure Airfield Control Group, or the Aerial Port of Embarkation. This mission requires the detachment to coordinate the loading and offloading of II MEF equipment and personnel from aircraft coming into and going out of Marine Corps Air Station, Cherry Point.