Federal Information Processing Standard state code

A two-digit Federal Information Processing Standard (FIPS) code (FIPS 5-2) uniquely identifies a state, territory, or commonwealth within or of the U.S.. These codes are used by the U.S. Census Bureau, by the Department of Agriculture to form milk-processing plant numbers, and in the Emergency Alert System, and were assigned by NIST. Additional numbers used with the EAS for territorial waters of the U.S. were assigned by the FCC, but are not part of the FIPS standard. Two-letter state codes were assigned as postal abbreviations by the USPS.

http://www.itl.nist.gov/fipspubs/fip5-2.htm

FIPS Code	State, territory, or commonwealth	Postal Abbreviation
01	Alabama	AL
02	Alaska	AK
04	Arizona	AZ
05	Arkansas	AR
06	California	CA
08	Colorado	CO
09	Connecticut	CT
10	Delaware	DE
11	District of Columbia	DC
12	Florida	FL
13	Georgia	GA
15	Hawaii	HI
16	Idaho	ID
17	Illinois	IL
18	Indiana	IN
19	Iowa	IA
20	Kansas	KS
21	Kentucky	KY
22	Louisiana	LA
23	Maine	ME
24	Maryland	MD
25	Massachusetts	MA
26	Michigan	MI
27	Minnesota	MN
28	Mississippi	MS
29	Missouri	MO
30	Montana	MT
31	Nebraska	NE
32	Nevada	NV
33	New Hampshire	NH
34	New Jersey	NJ
35	New Mexico	NM
36	New York	NY
37	North Carolina	NC
38	North Dakota	ND
39	Ohio	OH
40	Oklahoma	OK
41	Oregon	OR
42	Pennsylvania	PA
44	Rhode Island	RI
45	South Carolina	SC
46	South Dakota	SD
47	Tennessee	TN
48	Texas	TX
49	Utah	UT
50	Vermont	VT
51	Virginia	VA
53	Washington	WA
54	West Virginia	WV
55	Wisconsin	WI
56	Wyoming	WY
60	American Samoa	AS
64	Federated States of Micronesia	FM
66	Guam	GU
68	Marshall Islands	MH
69	Northern Mariana Islands	MP
70	Palau	PW
72	Puerto Rico	PR
74	U.S. Minor Outlying Islands	UM
78	Virgin Islands of the U.S.	VI

A common question is to ask why are there no State FIPS codes for 03, 07, 14, 43, and 52. These codes are now skipped, but originally were for:

(03) American Samoa, (07) Canal Zone, (14) Guam, (43) Puerto Rico, and (52) Virgin Islands. This caused a lot of difficulty as certain bureaus and agencies would have employees who could not quickly sort these territorial areas out. Thus, all (save for the Canal Zone, now part of Panama) were reassigned new numbers in the >60 range.