Service number (United States Marine Corps)

A service number, also historically referred to as an enlistment number, was a unique alphanumeric identifier assigned to each individual serving in the United States Marine Corps. Before the introduction of the Social Security Number (SSN) as a universal identifier, the service number served as the primary method of identifying Marine Corps personnel in official records, including pay, medical history, personnel files, and awards.

The format of the service number evolved over time. Early service numbers were purely numerical and relatively short. As the Marine Corps grew, the length of the service number increased to accommodate the larger number of personnel. During World War II and the Korean War, service numbers were typically seven digits long.

In the later half of the 20th century, the Marine Corps gradually phased out the use of service numbers in favor of the Social Security Number (SSN). The SSN offered the advantage of being a government-wide standard, simplifying administrative processes and data sharing with other federal agencies.

Although the SSN is now the primary identifier, service numbers still hold historical significance and are occasionally referenced in legacy documents and records. Veterans and historians may research service numbers to trace the service history of individual Marines. The National Archives and Records Administration (NARA) maintains records that may include service numbers.