Structure of Social Security Numbers
last modified May 15, 2001
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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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Area Numbers
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.
The following table is now out of date. The SSA currently maintains an
up-to-date version. I'm leaving the old one here in case the SSA's version
goes away. As of 2001/5/15, the SSA lists group numbers as high as 768 as
having 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.
As of Feb 10, 1999 the most recent area numbers to have been assigned
include 650-658, 667-675, and 680. This list is from the SSA's web site,
which shows the highest group number assigned for each area.
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NEW SSN LISTING:
The chart below shows the first 3 digits of the social security numbers
assigned throughout the United States and its possessions. See "Note" at
bottom of page.
001-003
New Hampshire
004-007
Maine
008-009
Vermont
010-034
Massachusetts
035-039
Rhode Island
040-049
Connecticut
050-134
New York
135-158
New Jersey
159-211
Pennsylvania
212-220
Maryland
221-222
Delaware
223-231
Virginia
691-699*
232-236
West Virginia
232
North Carolina
237-246
681-690
247-251
South Carolina
654-658
252-260
Georgia
667-675
261-267
Florida
589-595
766-772
268-302
Ohio
303-317
Indiana
318-361
Illinois
362-386
Michigan
387-399
Wisconsin
400-407
Kentucky
408-415
Tennessee
756-763*
416-424
Alabama
425-428
Mississippi
587-588
752-755*
429-432
Arkansas
676-679
433-439
Louisiana
659-665
440-448
Oklahoma
449-467
Texas
627-645
468-477
Minnesota
478-485
Iowa
486-500
Missouri
501-502
North Dakota
503-504
South Dakota
505-508
Nebraska
509-515
Kansas
516-517
Montana
518-519
Idaho
520
Wyoming
521-524
Colorado
650-653
525,585
New Mexico
648-649
526-527
Arizona
600-601
764-765
528-529
Utah
646-647
530
Nevada
680
531-539
Washington
540-544
Oregon
545-573
California
602-626
574
Alaska
575-576
Hawaii
750-751*
577-579
District of Columbia
580
Virgin Islands
580-584
Puerto Rico
596-599
586
Guam
586
American Samoa
586
Philippine Islands
700-728
Railroad Board**
729-733 Enumeration at Entry
NOTE: The same area, when shown more than once, means that certain numbers
have been transferred from one State to another, or that an area has been
divided for use among certain geographic locations.
Any number beginning with 000 will NEVER be a valid SSN.
The information in our records about an individual is confidential by law
and cannot be disclosed except in certain very restricted cases permitted by
regulations.
* = New areas allocated, but not yet issued
** 700-728 Issuance of these numbers to railroad employees was discontinued
July 1, 1963.
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Group Numbers
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
first.
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.
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Serial Numbers
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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Invalid SSNs
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 770
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 numbers.
This description of the structure of the Social Security Number is based on
messages written by Jerry Crow and Barbara Bennett. The information has been
verified by its correspondence to the SSA's Program Operations Manual System
(POMS) Part 01, Chapter 001, subchapter 01, which can be found at Federal
Depository Libraries. (SSA Pub. No. 68-0100201.)
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Source: http://www.cpsr.org/cpsr/privacy/ssn/ssn.structure.html
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