List of U.S. state abbreviations - wikipedia List of U.S. state abbreviations Several sets of codes and abbreviations are used to represent the political divisions of the United States for postal addresses, data processing, general abbreviations, and other purposes. Contents 1 Table 2 History 2.1 Current use of traditional abbreviations 3 Codes for states and territories 3.1 ISO standard 3166 3.2 ANSI standard INCITS 38 : 2009 3.3 Postal codes 3.4 Coast Guard vessel prefixes 4 See also 5 References 6 External links Table See also : List of states and territories of the United States This table includes abbreviations for three independent nations related to the United States through Compacts of Free Association, and other comparable postal abbreviations, including those now obsolete. Codes and abbreviations for U.S. states, territories, and other regions Codes : ISO ISO 3166 codes ( 2 - letter, 3 - letter, and 3 - digit codes from ISO 3166 - 1 ; 2 + 2 - letter codes from ISO 3166 - 2 ) ANSI 2 - letter and 2 - digit codes from the ANSI standard INCITS 38 : 2009 USPS 2 - letter codes used by the United States Postal Service USCG 2 - letter codes used by the United States Coast Guard ( red text shows differences between ANSI and USCG ) Abbreviations : GPO Older variable - length official US Government Printing Office abbreviations AP Abbreviations from the AP Stylebook ( red text shows differences between GPO and AP ) Name and status of region ISO ANSI USPS USCG GPO AP Other abbreviations United States of America Federal state US USA 840 US 00 U.S. U.S. U.S.A. Alabama State US - AL AL 01 AL AL Ala. Ala. Alaska State US - AK AK 02 AK AK Alaska Alaska Alas. Arizona State US - AZ AZ 04 AZ AZ Ariz. Ariz. Az. Arkansas State US - AR AR 05 AR AR Ark. Ark. California State US - CA CA 06 CA CF Calif. Calif. Ca., Cal. Colorado State US - CO CO 08 CO CL Colo. Colo. Col. Connecticut State US - CT CT 09 CT CT Conn. Conn. Ct. Delaware State US - DE DE 10 DE DL Del. Del. De. District of Columbia Federal district US - DC DC 11 DC DC D.C. D.C. Wash. D.C. Florida State US - FL FL 12 FL FL Fla. Fla. Fl., Flor. Georgia State US - GA GA 13 GA GA Ga. Ga. Hawaii State US - HI HI 15 HI HA Hawaii Hawaii H.I. Idaho State US - ID ID 16 ID ID Idaho Idaho Id., Ida. Illinois State US - IL IL 17 IL IL Ill. Ill. Il., Ills., Ill 's Indiana State US - IN IN 18 IN IN Ind. Ind. In. Iowa State US - IA IA 19 IA IA Iowa Iowa Ia., Ioa. Kansas State US - KS KS 20 KS KA Kans. Kan. Ks., Ka. Kentucky State ( Commonwealth ) US - KY KY 21 KY KY Ky. Ky. Ken., Kent. Louisiana State US - LA LA 22 LA LA La. La. Maine State US - ME ME 23 ME ME Maine Maine Me. Maryland State US - MD MD 24 MD MD Md. Md. Massachusetts State ( Commonwealth ) US - MA MA 25 MA MS Mass. Mass. Michigan State US - MI MI 26 MI MC Mich. Mich. Minnesota State US - MN MN 27 MN MN Minn. Minn. Mn. Mississippi State US - MS MS 28 MS MI Miss. Miss. Missouri State US - MO MO 29 MO MO Mo. Mo. Montana State US - MT MT 30 MT MT Mont. Mont. Nebraska State US - NE NE 31 NE NB Nebr. Neb. Nevada State US - NV NV 32 NV NV Nev. Nev. Nv. New Hampshire State US - NH NH 33 NH NH N.H. N.H. New Jersey State US - NJ NJ 34 NJ NJ N.J. N.J. N. Jersey New Mexico State US - NM NM 35 NM NM N. Mex. N.M. New M. New York State US - NY NY 36 NY NY N.Y. N.Y. N. York North Carolina State US - NC NC 37 NC NC N.C. N.C. N. Car. North Dakota State US - ND ND 38 ND ND N. Dak. N.D. NoDak Ohio State US - OH OH 39 OH OH Ohio Ohio O., Oh. Oklahoma State US - OK OK 40 OK OK Okla. Okla. Ok. Oregon State US - OR OR 41 OR OR Oreg. Ore. Or. Pennsylvania State ( Commonwealth ) US - PA PA 42 PA PA Pa. Pa. Penn., Penna. Rhode Island State US - RI RI 44 RI RI R.I. R.I. R.I. & P.P., R. Isl. South Carolina State US - SC SC 45 SC SC S.C. S.C. S. Car. South Dakota State US - SD SD 46 SD SD S. Dak. S.D. SoDak Tennessee State US - TN TN 47 TN TN Tenn. Tenn. Texas State US - TX TX 48 TX TX Tex. Texas Tx. Utah State US - UT UT 49 UT UT Utah Utah Ut. Vermont State US - VT VT 50 VT VT Vt. Vt. Virginia State ( Commonwealth ) US - VA VA 51 VA VA Va. Va. Virg. Washington State US - WA WA 53 WA WN Wash. Wash. Wa., Wn. West Virginia State US - WV WV 54 WV WV W. Va. W.Va. W.V., W. Virg. Wisconsin State US - WI WI 55 WI WS Wis. Wis. Wi., Wisc. Wyoming State US - WY WY 56 WY WY Wyo. Wyo. Wy. American Samoa Insular area ( Territory ) AS ASM 016 US - AS AS 60 AS AS A.S. Guam Insular area ( Territory ) GU GUM 316 US - GU GU 66 GU GU Guam Northern Mariana Islands Insular area ( Commonwealth ) MP MNP 580 US - MP MP 69 MP CM M.P. CNMI Puerto Rico Insular area ( Territory ) PR PRI 630 US - PR PR 72 PR PR P.R. U.S. Virgin Islands Insular area ( Territory ) VI VIR 850 US - VI VI 78 VI VI V.I. U.S.V.I. U.S. Minor Outlying Islands Insular areas UM UMI 581 US - UM UM 74 Baker Island island UM - 81 81 XB Howland Island island UM - 84 84 XH Jarvis Island island UM - 86 86 XQ Johnston Atoll atoll UM - 67 67 XU Kingman Reef atoll UM - 89 89 XM Midway Islands atoll UM - 71 71 QM Navassa Island island UM - 76 76 XV Palmyra Atoll atoll UM - 95 95 XL Wake Island atoll UM - 79 79 QW Micronesia Freely associated state FM FSM 583 FM 64 FM Marshall Islands Freely associated state MH MHL 584 MH 68 MH Palau Freely associated state PW PLW 585 PW 70 PW U.S. Armed Forces -- Americas US military mail code AA U.S. Armed Forces -- Europe US military mail code AE U.S. Armed Forces -- Pacific US military mail code AP Northern Mariana Islands Obsolete postal code CM Panama Canal Zone Obsolete postal code PZ PCZ 594 CZ Nebraska Obsolete postal code NB Philippine Islands Obsolete postal code PH PHL 608 PI Trust Territory of the Pacific Islands Obsolete postal code PC PCI 582 TT History As early as October 1831, the United States Post Office recognized common abbreviations for states and territories. However, they only accepted these abbreviations because of their popularity, preferring that patrons spell names out in full to avoid confusion. The traditional abbreviations for U.S. states and territories, widely used in mailing addresses prior to the introduction of two - letter U.S. postal abbreviations, are still commonly used for other purposes ( such as legal citation ), and are still recognized ( though discouraged ) by the Postal Service. Modern two - letter abbreviated codes for the states and territories originated in October 1963, with the issuance of Publication 59 : Abbreviations for Use with ZIP Code, three months after the Post Office introduced ZIP codes in July 1963. The purpose, rather than to standardize state abbreviations per se, was to make room in a line of no more than 23 characters for the city, the state, and the ZIP code. Since 1963, only one state abbreviation has changed. Originally Nebraska was `` NB '' ; but, in November 1969, the Post Office changed it to `` NE '' to avoid confusion with New Brunswick in Canada. The two - letter postal abbreviation system is complicated by the fact that several state names begin with the same letter ( e.g., eight state names begin with M and eight begin with N, four `` New '' and two `` North '' ). To avoid duplications, some abbreviations are not intuitive. Prior to 1987, when the U.S. Secretary of Commerce approved the two - letter codes for use in government documents, the United States Government Printing Office ( GPO ) suggested its own set of abbreviations, with some states left unabbreviated. Today, the GPO supports United States Postal Service standard. Current use of traditional abbreviations The Associated Press Stylebook, the usage guide for most United States newspapers, counsels the use of abbreviations for most state names, when appended to a city name ( for example, `` Santa Ana, Calif. '' ). AP suggests spelling out the names of Alaska, Hawaii, and all states with five or fewer letters ; and, unlike the old GPO recommendations, AP suggests spelling out the names of all non-state territories, with the exception of the District of Columbia ( D.C. ). Legal citation manuals, such as The Bluebook and The ALWD Citation Manual, typically use these `` traditional abbreviations '' or variants thereof. Codes for States and territories ISO standard 3166 Main article : ISO 3166 - 2 : US ANSI standard INCITS 38 : 2009 The American National Standards Institute ( ANSI ) established alphabetic and numeric codes for each state and outlying areas in ANSI standard INCITS 38 : 2009. ANSI standard INCITS 38 : 2009 replaced the Federal Information Processing Standard ( FIPS ) standards FIPS 5 - 2, FIPS 6 - 4, and FIPS 10 - 4. The ANSI alphabetic state code is the same as the USPS state code except for U.S. Minor Outlying Islands, which have an ANSI code `` UM '' but no USPS code -- and U.S. Military Mail locations, which have USPS codes ( `` AA '', `` AE '', `` AP '' ) but no ANSI code. Postal codes The United States Postal Service has established a set of uppercase abbreviations to help process mail with optical character recognition and other automated equipment. There are also official USPS abbreviations for other parts of the address, such as street designators ( street, avenue, road, etc. ). These postal abbreviations are distinguished from traditional abbreviations such as Calif., Fla., or Tex. The Associated Press Stylebook states that in contexts other than mailing addresses, the traditional state abbreviations should be used. However, the Chicago Manual of Style now recommends use of the uppercase two - letter abbreviations, with the traditional forms as an option. The postal abbreviation is the same as the ISO 3166 - 2 subdivision code for each of the fifty states. These codes do not overlap with the 13 Canadian subnational postal abbreviations. The code for Nebraska changed from NB to NE in November 1969 to avoid a conflict with New Brunswick. Canada likewise chose MB for Manitoba to prevent conflict with various U.S. states. Coast Guard vessel prefixes The U.S. Coast Guard ( USCG ) uses a set of two - letter prefixes for vessel numbers ; 39 states and the District of Columbia have the same USPS and USCG abbreviations. USCG prefixes have also been established for five outlying territories ; all are the same as the USPS abbreviations except the Mariana Islands. The twelve cases where USPS and USCG abbreviations differ are listed below and marked in red in the table above. Mis - matches between USPS and USCG codes California Colorado Delaware Hawaii Kansas Michigan Mississippi Massachusetts Nebraska Washington Wisconsin Mariana Islands USPS CA CO DE HI KS MI MS MA NE WA WI MP USCG CF CL DL HA KA MC MI MS NB WN WS CM See also Australian abbreviation system Canadian abbreviation system ISO 3166 - 2 : US United State Postal Service address formatting information References Jump up ^ `` Ioa. '' or ( more typically ) `` IOA '' found in Iowa post office cancellations from the 1870s. Jump up ^ `` search on WN ''. Digitum.washingtonhistory.org. Retrieved 2018 - 02 - 26. Jump up ^ `` Commonwealth of the Northern Mariana Islands ''. www.doi.gov. Retrieved 2018 - 01 - 07. ^ Jump up to : `` Geopolitical Entities, Names, and Codes Standard ''. NSG Standards Registry. Retrieved 2017 - 02 - 06. ^ Jump up to : The Palmyra Atoll is an unorganized incorporated territory of the United States that was previously a part of the Territory of Hawaii. Jump up ^ The U.S. Armed Forces -- Americas include the Caribbean Sea and exclude the United States, Canada, and Greenland. Jump up ^ The U.S. Armed Forces -- Europe include the Atlantic Ocean, the Mediterranean Sea, Canada, Greenland, Africa, and Southwest Asia. Jump up ^ The U.S. Armed Forces -- Pacific include the Indian Ocean, Oceania, and Asia except Southwest Asia. Jump up ^ Former USPS code `` CM '' for the Commonwealth of the Northern Mariana Islands is now obsolete ; it was changed to MP in 1988 to match ISO 3166 - 1. Jump up ^ Former USPS code `` NB '' for Nebraska is now obsolete ; it was changed to NE in November 1969 to avoid confusion with New Brunswick, Canada. Jump up ^ `` Philippine diplomats will now use PH or PHL instead of RP ''. GMA News. 28 October 2010. Retrieved 17 March 2013. ^ Jump up to : USPS Postal History : State Abbreviations Accessed November 7, 2011. Jump up ^ `` USPS Postal News, `` It 's Okay to Say ' I Do n't Know, ' So Long As You Find Out ! '' January 9, 2009 ``. About.usps.com. 2009 - 01 - 09. Retrieved 2018 - 02 - 26. Jump up ^ Hawes, Kristi G. ( 1987 - 05 - 28 ). `` Information Technology Laboratory ''. NIST. Retrieved 2009 - 04 - 21. Jump up ^ U.S. Government Printing Office Style Manual, 30th Edition ( 1 ) Accessed April 21, 2009. Jump up ^ United States Postal Service Publication 28 - Postal Addressing Standards. Accessed February 4, 2007. Jump up ^ State Abbreviations Jump up ^ Major Rule Changes in The Chicago Manual of Style, Fifteenth Edition Accessed May 23, 2009 Jump up ^ 33 C.F.R. 173, App. A External links USPS acronyms and abbreviations United States Postal Service Organizations American Letter Mail Company American Postal Workers Union Board of Governors of the United States Postal Service Bureau of Transportation Citizens ' Stamp Advisory Committee National Alliance of Postal and Federal Employees National Association of Letter Carriers National Association of Presort Mailers National Postal Mail Handlers Union National Rural Letter Carriers ' Association Postal Regulatory Commission Postal Transportation Service PostalWatch Incorporated United States Postal Inspection Service United States Postal Service Office of Inspector General Systems Address Management System Advanced Facer - Canceler System Coding Accuracy Support System Flats Sequencing System Locatable Address Conversion System United States Postal Savings System Services Click - N - Ship Express mail in the United States National Change Of Address Permit mail Permit Reply Mail Postal notes Railway Mail Service Registered mail Special Delivery Special handling Facilities Air Mail Facility Boat Railway Post Office Community post office Dead letter office Highway Post Office J.W. Westcott II List of United States Post Offices National Postal Museum Network Distribution Center Railway mail service library Red Brick Roads Sectional center facility Streetcar Railway Post Office Terminal Railway Post Office Legal Comstock laws Post Office Act Postal Reorganization Act Postal Service Act Private Express Statutes Rural Post `` Good '' Roads Act of 1916 Title 39 of the United States Code Related Airmails of the United States CAR - RT SORT Catcher pouch Cimarron Redoubt Domestic Mail Manual Facing Identification Mark Flats Grumman LLV Information - Based Indicia The Inspectors Intelligent Mail barcode Label 228 List of postal killings List of U.S. state abbreviations List of United States airmail stamps Mail bag Mail cover Mail hook Mail Isolation Control and Tracking Mail jumping Mail pouch Mail sack Mail satchel The Mail Story Nixie ORM - D Owney ( dog ) Pony Express mochila Postage stamps and postal history of the United States Postal Alpha Numeric Encoding Technique Postal Clause Postal worker Postmaster General Prohibitory Order Remote Bar Coding System Rural Free Delivery Rural letter carrier STD - 4C United States post office murals List of murals USPS Post Office Box Lobby Recycling program United States Postal Service creed United States state - related lists List of states and territories of the United States Demographics Educational attainment Irreligion Largest cities by population Most popular given names Most populous counties Population Density Growth rate Birth and death rates Historical African American Amish Asian Hispanic and Latino Spanish - speaking Religiosity Economy Billionaires Budgets Companies Federal tax revenue Federal taxation and spending Gross domestic product Growth rate Per capita Income Inequality Minimum wages Poverty rates Sales taxes Sovereign wealth funds State income taxes Unemployment rates Union affiliation Vehicles per capita Environment Carbon dioxide emissions Botanical gardens Parks Renewable energy Superfund sites Wilderness areas Geography Area Coastline Elevation Extreme points Forest Geographic centers Regions Government Attorneys general Capitals Capitol buildings Comparison Counties Alphabetical Current State Legislators Governors Lieutenant governors Legislatures Libraries and archives Official languages Poets laureate Political divisions State auditors State secretaries of state State superintendents of education State supreme courts State treasurers Health American Human Development Index Fertility rates Hospitals Life expectancy Obesity rates History Date of statehood Name etymologies Historical societies and museums National Historic Landmarks National Register of Historic Places State partitions Historic regions Law Abortion Age of consent Alcohol Dry communities Alford plea Cell phone use while driving Constitutions Firearms Homicide Law enforcement agencies Legality of cannabis Peace Index Prisons Incarceration rate Same - sex unions Former constitutional bans Marriage law Seat belt laws Self - representation Smoking bans Speed limits ( by jurisdiction ) Statutory codes Miscellaneous Abbreviations Demonyms Fictional states Flags Insignia License plates Numbered highways Quarters 50 states DC & Territories Symbols Tallest buildings Time zones Commons Portals Retrieved from `` https://en.wikipedia.org/w/index.php?title=List_of_U.S._state_abbreviations&oldid=845069853 '' Categories : Lists of states of the United States Lists of United States abbreviations Postal addresses in the United States Talk Contents About Wikipedia Català Čeština Esperanto Frysk Galego Ilokano Bahasa Indonesia 日本 語 Română Русский Simple English Slovenčina Slovenščina اردو Tiếng Việt 中文 8 more Edit links This page was last edited on 9 June 2018, at 04 : 10. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: when did state abbreviations change to two letters
Answer: October 1963