Security Number Information.
A Social Security Number (SSN)
consists of nine digits, commonly written as three fields separated
by hyphens: AAA-GG-SSSS. The first three-digit field is called the
"area number". The central, two-digit field is called the "group
number". The final, four-digit field is called the "serial number".
The process of assigning numbers has been
changed at least twice. Until 1965, only half the group numbers were
used. Before 1972, numbers were assigned by field offices; since
1972, they have all been assigned by the central office. The order
in which numbers were assigned was changed in the 1972 transition.
There may have been other changes, but it's difficult to get
information on how things used to be done.
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The area numbers are assigned to
geographical locations. They were originally assigned the same way
that zip codes were later assigned (in particular, area numbers
increase from east to west across the continental US as do the ZIP
codes). Most area numbers were assigned according to state (or
territorial) boundaries, although the series 700-729 was assigned to
railroad workers regardless of location (this series of area numbers
was discontinued in 1964 and is no longer used for new SSNs). Area
numbers assigned prior to 1972 are an indication of the SSA office
which originally issued the SSN. Since 1972 the area number in SSNs
corresponds to the residence address given by the applicant on the
application for the SSN.
In many regions the original range of area
number assignments was eventually exhausted as population grew. The
original area number assignments have been augmented as required.
All of the original assignments were less than 585 (except for the
700-729 railroad worker series mentioned above). Area numbers of
"000" have never been issued.
001-003 NH 400-407 KY 530 NV
004-007 ME 408-415 TN 531-539 WA
008-009 VT 416-424 AL 540-544 OR
010-034 MA 425-428 MS 545-573 CA
035-039 RI 429-432 AR 574 AK
040-049 CT 433-439 LA 575-576 HI
050-134 NY 440-448 OK 577-579 DC
135-158 NJ 449-467 TX 580 VI Virgin Islands
159-211 PA 468-477 MN 581-584 PR Puerto Rico
212-220 MD 478-485 IA 585 NM
221-222 DE 486-500 MO 586 PI Pacific Islands*
223-231 VA 501-502 ND 587-588 MS
232-236 WV 503-504 SD 589-595 FL
237-246 NC 505-508 NE 596-599 PR Puerto Rico
247-251 SC 509-515 KS 600-601 AZ
252-260 GA 516-517 MT 602-626 CA
261-267 FL 518-519 ID 627-645 TX
268-302 OH 520 WY 646-647 UT
303-317 IN 521-524 CO 648-649 NM
318-361 IL 525 NM *Guam, American Samoa,
362-386 MI 526-527 AZ Philippine Islands,
387-399 WI 528-529 UT Northern Mariana Islands
650-699 unassigned, for future use
700-728 Railroad workers through 1963, then discontinued
729-799 unassigned, for future use
800-999 not valid SSNs. Some sources have claimed that numbers
above 900 were used when some state programs were converted
to federal control, but current SSA documents claim no
numbers above 799 have ever been used.
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The group number is not related to
geography but rather to the order in which SSNs are issued for a
particular area. Before 1965, only half the group numbers were used:
odd numbers were used below 10 and even numbers were used above 9.
In 1965 the system was changed so assignments continued with the low
even numbers and the high odd numbers. So, group numbers for each
area number are assigned in the following order:
- Odd numbers, 01 to 09
- Even numbers, 10 to 98
- Even numbers, 02 to 08
- Odd numbers, 11 to 99
Group codes of "00" aren't assigned
In each region, all possible area numbers
are assigned with each group number before using the next group
number. This means the group numbers can be used to find a
chronological ordering of SSNs within a region. When new group
numbers are assigned to a state, the old numbers are usually used up
SSA publishes a list every month of the
highest group assigned for each SSN Area. For example, if the
highest group assigned for area 999 is 72, then we know that the
number 999-04-1234 is an invalid number because even Groups under 9
have not yet been assigned.
Serial numbers are assigned in
chronological order within each area and group number as the
applications are processed. Serial number "0000" is never used.
Before 1965, when number assignment was transferred from field
offices to the central office, serial numbers may have been assigned
in a strange order. (Some sources claim that 2000 and 7000 series
numbers were assigned out of order. That no longer seems to be the
case.) Currently, the serial numbers are assigned in strictly
increasing order with each area and group combination.
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Any SSN conforming to one of the following
criteria is an invalid number:
- Any field all zeroes (no field of
zeroes is ever assigned).
- First three digits above 740
A pamphlet entitled "The Social Security
Number" (Pub. No. 05-10633) provides an explanation of the SSN's
structure and the method of assigning and validating Social Security