State Abbreviations

List of State Abbreviations

As early as October 1874, the United States Post Office recognized common abbreviations for states and territories.

Modern two-letter abbreviated codes for the states and territories originated when the Post Office introduced ZIP codes in 1963. The purpose was to make room for ZIP codes in the address, rather than to standardize state abbreviations per se.

The two-letter postal abbreviation system is complicated by the fact that eight state names begin with M and to avoid duplication, some abbreviations are not intuitive.

State Abbreviations

Alabama: AL	Montana: MT
Alaska: AK	Nebraska: NE
Arizona: AZ	Nevada: NV
Arkansas: AR	New Hampshire: NH
California: CA	New Jersey: NJ
Colorado: CO	New Mexico: NM
Connecticut: CT	New York: NY
Delaware: DE	North Carolina: NC
Florida: FL	North Dakota: ND
Georgia: GA	Ohio: OH
Hawaii: HI	Oklahoma: OK
Idaho: ID	Oregon: OR
Illinois: IL	Pennsylvania: PA
Indiana: IN	Rhode Island: RI
Iowa: IA	South Carolina: SC
Kansas: KS	South Dakota: SD
Kentucky: KY	Tennessee: TN
Louisiana: LA	Texas: TX
Maine: ME	Utah: UT
Maryland: MD	Vermont: VT
Massachusetts: MA	Virginia: VA
Michigan: MI	Washington: WA
Minnesota: MN	West Virginia: WV
Mississippi: MS	Wisconsin: WI
Missouri: MO	Wyoming: WY

List by Abbreviations

AK: Alaska	MT: Montana
AL: Alabama	NC: North Carolina
AR: Arkansas	ND: North Dakota
AZ: Arizona	NE: Nebraska
CA: California	NH: New Hampshire
CO: Colorado	NJ: New Jersey
CT: Connecticut	NM: New Mexico
DE: Delaware	NV: Nevada
FL: Florida	NY: New York
GA: Georgia	OH: Ohio
HI: Hawaii	OK: Oklahoma
IA: Iowa	OR: Oregon
ID: Idaho	PA: Pennsylvania
IL: Illinois	RI: Rhode Island
IN: Indiana	SC: South Carolina
KS: Kansas	SD: South Dakota
KY: Kentucky	TN: Tennessee
LA: Louisiana	TX: Texas
MA: Massachusetts	UT: Utah
MD: Maryland	VA: Virginia
ME: Maine	VT: Vermont
MI: Michigan	WA: Washington
MN: Minnesota	WI: Wisconsin
MO: Missouri	WV: West Virginia
MS: Mississippi	WY: Wyoming

The U.S. Standardized Two-Letter State Abbreviations

When you write an address in the United States, you likely use a two-letter code such as CA for California, NY for New York or TX for Texas. These codes are so commonplace that we take them for granted. Yet, they are the product of a deliberate standardization process—driven largely by the needs of the national postal system and of efficient addressing. Understanding why and how these abbreviations came about tells us something about communication, geography, administration, and modernization in the United States.

The need for abbreviations: practical origins

From the earliest days of the U.S., when states or territories were referenced in writing, people often abbreviated state names informally. Long state names (e.g., “Massachusetts,” “Connecticut,” “Tennessee”) made abbreviations a convenience for correspondence, record-keeping, and printing. But convenience was not the only driver: as the volume of mail and the complexity of addressing grew in the 19th and 20th centuries, the postal system sought ways to streamline processing.

In 1831, the then-Post Office Department (which later became the United States Postal Service, or USPS) recognized a list of preferred state and territory abbreviations. Many of these abbreviations were short (two to four letters) but not uniform. For example, Virginia might be “Va.”, Massachusetts “Mass.”, and so on. The fact of having a recognized list rather than purely ad hoc abbreviations already shows that standardization was beginning to matter.

Early formal lists

By 1874, the Post Office Department had updated its list of state abbreviations in the United States Official Postal Guide. These abbreviations still varied in length (often three or four letters), and the policy of the Post Office was to print state names in full (i.e., “California,” “Arkansas”) in preference to abbreviations whenever possible, to avoid confusion. But given the realities of typesetting, address lines, and space constraints, informal or shortened forms continued to be used by senders.

Thus, by the early 20th century one had a mixture of: (1) full state names, (2) semi-standard abbreviations (e.g., “Calif.”, “Conn.”), and (3) varying practices depending on publisher, state, or context (legal citations, newspapers, mail).

The trigger: ZIP Codes and addressing constraints

A major impetus for revising state-abbreviation practice came in the mid-20th century with the introduction of the ZIP Code system. On July 1, 1963, the Post Office Department introduced the five-digit ZIP (Zone Improvement Plan) code. The idea was to speed mail sorting and delivery by giving each postal region a numeric code. But adding the ZIP Code also meant that the “city-state-ZIP” portion of an address line would grow in length.

According to the USPS history, most addressing equipment at the time could accommodate only 23 characters (including spaces) in the bottom line of the address. To make room for the ZIP Code, the state name (or its abbreviation) had to be shortened. If the state name was fully spelled out (e.g., “Massachusetts”), plus a space, plus the five-digit ZIP, the total could exceed the limit. The Post Office Department therefore issued new guidelines to shorten the state portion.

In June 1963, an initial list of abbreviations (many of them three or four letters) was provided. But the Department found that many of them were still too long to reliably fit within the addressing equipment constraints. Accordingly, in October 1963 the Department settled on a uniform set of two-letter uppercase abbreviations with no periods or spaces between letters (e.g., “CA”, “NY”, “TX”).

Thus, the adoption of two-letter state abbreviations is directly linked to the rise of automated and mechanized mail sorting and the need to standardize address lines for machine readability.

Why two letters? and how the letters were chosen

Why choose exactly two letters? Several factors influenced this decision:

• Efficiency: Two characters take less space, enabling the ZIP Code and city name to fit in the allowed character limit.
• Uniformity: Having all states use the same format (two uppercase letters) avoids confusion and simplifies data processing, filing systems, and computerized databases.
• Distinction: Two letters are usually sufficient to distinguish 50 different items (the 50 states) provided the choices avoid duplication.
• Legacy: The postal department already had abbreviations of three or four letters; reducing to two was the next logical step to minimize length while retaining recognizability.

How were the individual two-letter codes chosen? The selection generally followed a number of principles:

1. Use the first two letters of the name when possible (e.g., AL = Alabama, AK = Alaska).
2. When the first two letters would duplicate an existing code (or be too ambiguous), alternative letters were used—sometimes the first and last letter, or a prominent consonant from the name. For example, Montana became MT instead of MO (which was used by Missouri) or MA (used by Massachusetts).
3. Avoid confusion with other states and with territories or foreign jurisdictions. For instance, Nebraska originally had the abbreviation “NB” in 1963, but in 1969 it was changed to “NE” at the request of Canada (to avoid confusion with New Brunswick).
4. Standard formats: all uppercase, no punctuation, exactly two letters.

Thus the system provides codes that are quickly recognizable, distinct from one another, and formatted uniformly.

Implementation and official adoption

In October 1963, the Post Office Department published Publication 59: Abbreviations for Use with ZIP Code, which formalized the new two-letter codes. From that point onward, the two-letter abbreviations became the official postal standard for addressing mail in the U.S.

Though in practice it took some years for all print materials, reference works, addressing guides, and public usage to adopt the new codes, the shift was underway in the 1960s and became dominant in the 1970s and afterward.

Since the initial adoption, there has been only one change: Nebraska’s change from NB to NE in 1969.

Other abbreviation systems and traditional forms

It is worth noting that the USPS two-letter codes are not the only abbreviations ever used. In many contexts—legal citations, newspapers, datelines, academic writing, historic documents—traditional abbreviations (often three to five letters, with periods) persist. For example, “Mass.” for Massachusetts, “Conn.” for Connecticut, “Tenn.” for Tennessee, “Calif.” for California. These are still recognized though discouraged for mailing purposes.

Different style guides (AP, Chicago, MLA) have distinct conventions for when to use full state names, traditional abbreviations, or postal abbreviations. The postal abbreviations are primarily designed for addressing mail; they are not necessarily mandated in all prose.

Why standardization mattered (and still matters)

Several key reasons explain why a standardized two-letter abbreviation system became, and remains, important:

• Mail sorting and automation: As mail volumes grew and sorting processes became mechanized, uniformity in address formatting became crucial. Two-letter codes allowed machines and clerks to quickly recognize state identifiers, reducing errors and speed. The ZIP Code system itself was part of this mechanization.
• Data processing & record-keeping: Government agencies, businesses, and databases need standard codes for states. A uniform two-letter system is easy to parse, sort, and integrate into computer systems, reducing ambiguity and variation.
• Space efficiency: Printed materials, labels, forms, and address lines often have limited space. Shorter abbreviations mean more compact, legible addresses and less crowding.
• Inter-agency and inter-departmental consistency: If different agencies used many different abbreviations, confusion would arise. Standard codes enable consistency across federal, state, and local levels, as well as across private sector uses.
• Avoiding duplication and confusion: With 50 states plus territories, careful design of codes reduces the chance that two state names would share the same abbreviation (or that a state’s code would conflict with another’s). The standardization effort helped minimize such conflicts.
• International / inter-jurisdictional clarity: As postal communications cross state and national borders, the codes help ensure that letters are routed correctly. The Nebraska change is one small example of international clarity concerns.

The broader historical perspective

The evolution of U.S. state abbreviations reflects broader themes of modernization and standardization in American history. In the 19th century, the U.S. was becoming increasingly interconnected via railroads, telegraph, and postal systems. The growth of national institutions (including the Post Office) demanded greater uniformity. Typography, printing, and forms all shaped how state names and abbreviations were used.

In the 20th century, with the rise of mass mailings, automatic sorting machines, computer records, and national census data, legacy informal abbreviations were inadequate. The shift in 1963 to a machine-friendly two-letter standard marked the transition into the era of digital/automated data processing. One might say that the postal abbreviation system is a small but telling example of how administrative infrastructure becomes standardized to support large-scale public and private systems.

Some complications & quirks

Despite the broad standardization, there are still a few interesting quirks worth mentioning:

• Some states’ abbreviations don’t follow a pure “first two letters” rule (e.g., Missouri = MO rather than MS, because Mississippi took MS).
• Because many states begin with the same letter (for example, eight states begin with “M,” eight with “N”), the system had to manage potential conflicts by selecting second letters or different strategies.
• Traditional abbreviations persist in certain styles and contexts (for example, in datelines, bibliographies, or older documents).
• Territories and military mail have special abbreviation sets (such as “AA,” “AE,” “AP” for armed-forces addresses).
• Although the standard was issued in 1963, adoption in practice across every institution took time; many people continued using legacy abbreviations into the 1970s and beyond.

Case study: Nebraska’s change

A useful case to illustrate the interplay of standardization and international clarity is the case of Nebraska. When the USPS issued its two-letter codes in October 1963, Nebraska’s code was “NB.” However, Canada’s postal administration objected, pointing out that “NB” was also the abbreviation for the Canadian province of New Brunswick.

To prevent confusion in cross-border mail, the USPS in 1969 changed Nebraska’s code to “NE.” This illustrates how even within a national system, external factors (international mail, Manitoba/New Brunswick overlap, etc.) influenced abbreviation choices.

The current system in use

Since 1963, and the 1969 change, the postal two-letter abbreviations have remained remarkably stable. This stability signals that the design met its functional requirements: minimal length, distinctiveness, ease of use, international clarity, and compatibility with automated systems.

In practice today:

• When addressing mail in the U.S., the USPS requires the use of the two-letter code (in uppercase, no punctuation) for the state/territory portion of the address line.
• Many databases, forms, government documents, and geographic information systems adopt the two-letter code as the standard state identifier.
• While people still sometimes use traditional abbreviations in prose (“Mass.”, “Conn.”, ‘Mich”, etc.), many style guides encourage spelling the state name in full, unless space is constrained (as in addresses).
• The two-letter codes are deeply embedded in workflows (shipping, logistics, e-commerce, government reporting).

Why this matters: implications and reflections

On the surface, state abbreviations might seem like a minor typographical detail. But their design and implementation reflect several broader themes:

• Standardization as infrastructure: The system shows how seemingly trivial standards (two letters) are part of the infrastructure of communication. Without standard codes, automating tasks (like mail sorting) or integrating databases would be far more error-prone.
• Efficiency and scale: As the U.S. population, economy, and flow of mail expanded, the old informal abbreviations were inadequate for rapid sorting, handling of high volumes, and machine-readability. The shift to two letters is a small piece of the larger automation trend of the 20th century.
• Design trade-offs: Choosing two letters required balancing recognizability (so recipients know what state is meant) with brevity (so space constraints are satisfied). It also required avoiding duplication and preventing confusion with other jurisdictions. Thus, the choices of letters reflect rules and exceptions.
• Legacy and transition: Because the change was fairly recent (1963) many older documents and practices still reflect the legacy forms. Recognizing this helps understand older maps, address books, newspaper datelines, legal citations, and so on.
• Symbolism of federal-state coordination: The system is a federal standard (USPS) but is used at all levels of government and by private actors. It exemplifies how federal institutions provide standardization scaffolding that state and local governments adopt.
• Global connections: The Nebraska-New Brunswick example shows that even domestic standards must sometimes account for international or cross-border realities.

Criticisms or limitations

While the current system works well, it is not perfect or without quirks:

• Some codes are less intuitive than others (e.g., “WY” for Wyoming rather than “WO ” makes sense, but “MO” for Missouri and “MT” for Montana can confuse those unfamiliar; “MI” and “MS” for Michigan and Mississippi require memorization).
• Some academic or editorial contexts prefer full state names or traditional abbreviations, which can lead to inconsistency when comparing with postal formats.
• In everyday prose writing, the two-letter codes can seem abrupt or overly “code-like”; many style guides still discourage use of postal abbreviations outside addresses.
• The system pertains primarily to the 50 states (and some territories); other jurisdictions (such as ISO 3166 codes, country codes, etc.) follow different rules, which can pose a challenge in global systems.
• The reliance on two letters means that states with very similar initial letters had to adopt less obvious second letters; for newcomers or non-residents the logic can feel opaque.

On Reflection

The story of U.S. state abbreviations is more than a typographical curiosity. It is a story of how increasing complexity in communication (especially mail), the demands of automation and data systems, and the need for national standardization combined to produce a simple but effective solution: two-letter uppercase codes for each state.

The implementation of this standard in October 1963 by the Postal Service was a watershed moment: it shortened and unified the abbreviations used across the country, made space for the ZIP Code, and helped prepare the U.S. system of addressing and record-keeping for the modern era.

Although traditional abbreviations still linger in historic and stylistic contexts, the two-letter codes remain the backbone of how we identify states in data, shipping, administration, and daily correspondence. They remind us that even small typographic conventions are part of the architecture of communication, bridging human readability, machine processing, and scale.

In short: we abbreviate the states because it was necessary; we chose two letters because it was efficient; we settled on the particular letters because they balanced clarity and distinctiveness; and we adopted the system because the national postal system required it in an age of increasing volume and mechanization.

Today, those two letters connect us to a long evolution of the American postal and administrative infrastructure.