The Social Security Board quickly established registration offices to handle the registration of individuals and the assignment of Social Security numbers (SSN). In 1972, assignment of the numbers was centralized in the Baltimore office. More than 450 million numbers have been issued to date, and none is ever replicated. Each SSN has nine digits, subdivided into three groups:
Area Number (three digits)
Group Number (two digits)
Serial Number (four digits)
The first group is the one most pertinent to genealogical research. This is the area number. Each state was assigned groups of numbers.
This number does not necessarily reflect the state of residence of the individual. Since the beginning, one could always register for an SSN at any office. Prior to 1972, the area number reflects the state in which the office where one registered was located. Although a resident of Massachusetts, the closest office to me was across the border in Rhode Island. Had I registered prior to 1972, my area number would be between 035 and 039.
The rules changed once assignment was centralized in 1972. From that point forward, the number was assigned based on the zip code in the mailing address for the individual. Once again, this may not necessarily be the state of residence.
Numbers between 700 and 728 were assigned to the Railroad Retirement Board (RRB). The RRB was created a year earlier than Social Security to deal specifically with retirement benefits for those working in the rail industry. Because these individuals did not receive benefits from the SSA, earlier deaths do not appear in the DMF. Records of the RRB start in 1936, and are accessed through the National Archives. More information is available on the RRB website.
In an effort to prolong the use of nine-digit SSNs, and for security purposes, the Social Security Administration began a new process on June 25, 20011. The “SSN Randomization” methodology now renders this number useless for determining the location of registration.