Social Security Number Structure Chart

The Social Security Number Has Three Parts

The nine-digit SSN is composed of three parts:

• The first set of three digits is called the Area Number
• The second set of two digits is called the Group Number
• The final set of four digits is the Serial Number

Area Number

The Area Number is assigned by the geographical region. Prior to 1972, cards were issued in local Social Security offices around the country and the Area Number represented the State in which the card was issued. This did not necessarily have to be the State where the applicant lived, since a person could apply for their card in any Social Security office. Since 1972, when SSA began assigning SSNs and issuing cards centrally from Baltimore, the area number assigned has been based on the ZIP code in the mailing address provided on the application for the original Social Security card. The applicant's mailing address does not have to be the same as their place of residence. Thus, the Area Number does not necessarily represent the State of residence of the applicant, either prior to 1972 or since.

Generally, numbers were assigned beginning in the northeast and moving westward. So people on the east coast have the lowest numbers and those on the west coast have the highest numbers.

Note: One should not make too much of the "geographical code." It is not meant to be any kind of useable geographical information. The numbering scheme was designed in 1936 (before computers) to make it easier for SSA to store the applications in our files in Baltimore since the files were organized by regions as well as alphabetically. It was really just a bookkeeping device for our own internal use and was never intended to be anything more than that.

 Group Number

Within each area, the group number (middle two (2) digits) range from 01 to 99 but are not assigned in consecutive order. For administrative reasons, group numbers issued first consist of the ODD numbers from 01 through 09 and then EVEN numbers from 10 through 98, within each area number allocated to a State. After all numbers in group 98 of a particular area have been issued, the EVEN Groups 02 through 08 are used, followed by ODD Groups 11 through 99.

Serial Number

Within each group, the serial numbers (last four (4) digits) run consecutively from 0001 through 9999.

The First Card & the Lowest Number
The full story of who got the first Social Security card (and when) and who received the lowest number, and why.

SSNs Issued By Woolworth?
The story of the most misused Social Security number in history.

The SSN "Dog Tag" Story
The plan that never was.

The Design of the Social Security Card
The story of the man who designed the Social Security card.

The SSN Numbering Scheme
The first three digits of the SSN are a geographical code.

Forms and Explanatory Materials Used in 1936
Images of the forms and explanatory materials used in the original Social Security number issuance process in late 1936.

1953 Pamphlet
Pamphlet issued to the public in 1953 to explain the purpose and use of the SSN.

Significant Milestones in Social Security Number Policy
A detailed chronology of the major changes in policy and procedures 1936-1999.

New Social Security Numbers Issued Year-by-Year
A table of annual volumes.