Introduction
Accurate region selection (state/province/territory) is a core dependency for shipping, billing, tax calculation, and address validation. In professional systems, the region is typically stored as a standardized two-character code (for example, USPS state abbreviations like CA or Canada Post province abbreviations like QC) rather than a full name to avoid inconsistencies and improve data integrity.
This guide consolidates U.S. states, U.S. territories/possessions, U.S. military mail “states,” and Canadian provinces/territories, with the official two-letter abbreviations used in databases, carrier integrations, and e-commerce checkout forms. For authoritative references, see USPS Pub 28: State Abbreviations and Canada Post: Province/Territory abbreviations.
TL;DR: Store regions as official two-letter codes (USPS/Canada Post) to reduce validation errors and improve compatibility with shipping, ERP/CRM, and tax engines.
ZIP Codes vs. Canadian Postal Codes (Terminology and Validation)
A ZIP Code (Zone Improvement Plan) is a U.S.-only postal code system managed by the United States Postal Service (USPS). Canada uses postal codes exclusively, managed by Canada Post. Avoid labeling Canadian postal codes as “ZIP” in UI fields, APIs, or database columns—this commonly causes user confusion and downstream validation issues.
High-level structure differences:
- U.S. ZIP Code: typically 5 digits (e.g.,
94105) or ZIP+4 (9 digits, often written94105-1234). Validation is usually numeric-only with optional hyphen for ZIP+4. - Canadian postal code: alternating letter-number-letter + space + number-letter-number (e.g.,
K1A 0B1). Validation is typically uppercase A–Z with specific letter restrictions in certain positions.
For official formatting guidance, see USPS Publication 28 and Canada Post Addressing Guidelines.
TL;DR: ZIP Codes are U.S.-only (5 or 9 digits). Canada uses postal codes (A1A 1A1). Use separate validation rules to prevent bad data.
USPS State Abbreviations (U.S. States, DC, Territories, and Military “States”)
Most shipping systems and “state code to ZIP code mapping” reference tables use the official USPS state abbreviations (two characters) as the region key. This includes the 50 states, Washington, D.C. (DC), U.S. territories, and military mail regions (AA/AE/AP) used with APO/FPO/DPO addresses.
U.S. States + District of Columbia (USPS two-letter codes)
| Region | USPS Code |
|---|---|
| Alabama | AL |
| Alaska | AK |
| Arizona | AZ |
| Arkansas | AR |
| California | CA |
| Colorado | CO |
| Connecticut | CT |
| Delaware | DE |
| Florida | FL |
| Georgia | GA |
| Hawaii | HI |
| Idaho | ID |
| Illinois | IL |
| Indiana | IN |
| Iowa | IA |
| Kansas | KS |
| Kentucky | KY |
| Louisiana | LA |
| Maine | ME |
| Maryland | MD |
| Massachusetts | MA |
| Michigan | MI |
| Minnesota | MN |
| Mississippi | MS |
| Missouri | MO |
| Montana | MT |
| Nebraska | NE |
| Nevada | NV |
| New Hampshire | NH |
| New Jersey | NJ |
| New Mexico | NM |
| New York | NY |
| North Carolina | NC |
| North Dakota | ND |
| Ohio | OH |
| Oklahoma | OK |
| Oregon | OR |
| Pennsylvania | PA |
| Rhode Island | RI |
| South Carolina | SC |
| South Dakota | SD |
| Tennessee | TN |
| Texas | TX |
| Utah | UT |
| Vermont | VT |
| Virginia | VA |
| Washington | WA |
| West Virginia | WV |
| Wisconsin | WI |
| Wyoming | WY |
| District of Columbia (Washington, DC) | DC |
U.S. Territories, Possessions, and Compact-of-Free-Association ZIP participants
Many territories have their own USPS two-letter codes and use U.S. ZIP Codes. Additionally, some independent countries (Federated States of Micronesia, Marshall Islands, Palau) use U.S. ZIP Codes under Compact of Free Association agreements—implementers should treat these carefully in country/region logic (they may be “FM/MH/PW” region codes but are not “US” as a country in every data model).
| Region | USPS Code | Notes |
|---|---|---|
| American Samoa | AS | U.S. territory; uses U.S. ZIP Codes |
| Federated States of Micronesia | FM | Independent; uses U.S. ZIP Codes (compact agreement) |
| Guam | GU | U.S. territory; uses U.S. ZIP Codes |
| Marshall Islands | MH | Independent; uses U.S. ZIP Codes (compact agreement) |
| Northern Mariana Islands | MP | U.S. commonwealth; uses U.S. ZIP Codes |
| Palau | PW | Independent; uses U.S. ZIP Codes (compact agreement) |
| Puerto Rico | PR | U.S. territory; uses U.S. ZIP Codes |
| U.S. Virgin Islands | VI | U.S. territory; uses U.S. ZIP Codes |
U.S. Military Mail Regions (AA/AE/AP) for APO/FPO/DPO address formats
Military mail uses “state-like” region codes with APO (Army/Air Post Office), FPO (Fleet Post Office), or DPO (Diplomatic Post Office). In forms, the city field is typically APO/FPO/DPO, and the region/state field is one of the following USPS military codes:
| Military Region Name | USPS Code | Typical Geographic Coverage (routing category) |
|---|---|---|
| Armed Forces Americas | AA | Americas (excluding Canada), incl. some diplomatic/military routes |
| Armed Forces Europe | AE | Europe, Middle East, Africa, and Canada (per USPS routing conventions) |
| Armed Forces Pacific | AP | Pacific region (e.g., Asia-Pacific) |
Authoritative background: USPS Pub 28: APO/FPO/DPO addressing.
TL;DR: Use USPS two-letter codes everywhere (including DC, territories, and AA/AE/AP). APO/FPO/DPO addresses rely on these codes for correct routing and validation.
Canada Post Province Abbreviations (Provinces and Territories)
Canada uses postal codes (not ZIP Codes) and standard two-letter region abbreviations maintained by Canada Post. In enterprise systems, store the province/territory as a two-character code (e.g., ON, QC) and keep “country” as a separate field (e.g., CA for Canada) to avoid inconsistent labels like “Alberta, Canada.”
| Province/Territory | Canada Post Code | Example Postal Code Prefix (first character) |
|---|---|---|
| Alberta | AB | T |
| British Columbia | BC | V |
| Manitoba | MB | R |
| New Brunswick | NB | E |
| Newfoundland and Labrador | NL | A |
| Nova Scotia | NS | B |
| Ontario | ON | K / L / M / N / P |
| Prince Edward Island | PE | C |
| Quebec | QC | G / H / J |
| Saskatchewan | SK | S |
| Northwest Territories | NT | X |
| Nunavut | NU | X |
| Yukon | YT | Y |
Reference: Canada Post province/territory abbreviations.
TL;DR: Canada Post uses official two-letter province/territory codes (e.g., QC, NL, YT). Keep country separate and validate postal codes as A1A 1A1.
Using These Regions in ZIP and Postal Code Systems (Database and Integration Notes)
In most databases, region codes function as a two-character field (e.g., CHAR(2)) linked to a reference table (dimension) such as state_province. This supports consistent joins for carrier rating, “state code to ZIP code mapping,” tax jurisdiction logic, and standardized reporting.
- Data integrity: storing full names (“California”) alongside abbreviations (“CA”) increases duplicates and mismatches; standardizing on codes reduces ambiguity.
- Validation: enforce country-aware validation (US ZIP numeric vs. CA postal alphanumeric). Do not validate Canadian postal codes with U.S. ZIP regex rules.
- Territory and compact edge cases: FM/MH/PW use U.S. ZIP codes but are not U.S. states; your country field and compliance rules may need special handling.
If you need official abbreviations for software and addressing logic, start with USPS state abbreviations and Canada Post’s abbreviation list cited above.
TL;DR: Implement region as a 2-character code with a reference table, validate ZIP vs. postal code by country, and treat FM/MH/PW carefully in country logic.
Common Implementation Use Cases (Shipping, ERP/CRM, Tax Engines)
This reference is commonly used in:
- Shipping software: ensuring USPS state abbreviations and Canada Post province abbreviations match carrier expectations; improving label generation and routing.
- ERP/CRM systems: standardizing account addresses to prevent duplicate customer records and failed integrations.
- Tax calculation engines: mapping jurisdiction rules (state/province + postal/ZIP) for rate determination, exemptions, and reporting.
- Checkout/address forms: providing dropdowns keyed by official two-letter codes to reduce user input variation and improve deliverability.
TL;DR: Standard region codes power reliable shipping, clean master data in ERP/CRM, and accurate tax jurisdiction mapping.
Address Format Examples (Including APO/FPO and Canada)
Use these as “known-good” examples when testing form field mappings (address1, city, region, postal_code, country) and carrier integrations.
Example: Properly formatted U.S. address
Jane Doe
123 Market St
San Francisco, CA 94105
UNITED STATES
Example: Properly formatted APO/FPO (military) address
SGT John Doe
PSC 123 Box 4567
APO, AE 09012
UNITED STATES
Example: Properly formatted Canadian address
Alex Smith
123 Main St W
Ottawa, ON K1A 0B1
CANADA
TL;DR: U.S. uses state code + ZIP; APO/FPO uses AA/AE/AP; Canada uses province code + postal code (A1A 1A1).
Conclusion
For production systems, the most reliable approach is to store and validate regions using official two-letter codes: USPS for U.S. states/territories/military regions and Canada Post for provinces/territories. This improves “state code to ZIP code mapping,” reduces address normalization errors, and increases compatibility across carriers, ERPs/CRMs, and tax calculation platforms.
TL;DR: Standardize on official two-letter region codes and country-aware ZIP/postal validation for cleaner data and fewer shipping failures.
FAQ
Q: Where can I find the official USPS state abbreviations list?
A: USPS publishes the official two-letter abbreviations in Publication 28. A commonly referenced table is available here: USPS Pub 28 – State Abbreviations.
Q: What is the difference between state names and state abbreviations in address forms?
A: State names are human-readable (“California”), while abbreviations are standardized codes (“CA”) required by many shipping and validation systems. A common best practice is to store the two-letter code as the canonical value and optionally display the full name in the UI via a reference table.
Q: Do U.S. territories have ZIP codes, and is there a US territory ZIP code list?
A: Yes—many U.S. territories (e.g., PR, GU, VI, AS, MP) use U.S. ZIP Codes. If you need a “US territory ZIP code list,” use USPS addressing references and ensure your system supports territory codes (PR, GU, VI, AS, MP) in the region field.
Q: What are the AA, AE, and AP codes, and how do APO FPO DPO address formats work?
A: AA/AE/AP are USPS military region codes used with APO/FPO/DPO “city” values. AE generally covers Europe/Middle East/Africa routing categories, AP covers Pacific, and AA covers the Americas routing category. These codes are essential for validation and correct routing in military mail.
Q: What are Canada Post province abbreviations, and how should I validate Canadian postal codes?
A: Canada Post province/territory abbreviations are two-letter codes like ON, QC, and NL. Canadian postal codes use the A1A 1A1 pattern (letters and digits). Validate postal codes with Canada-specific rules and do not apply U.S. ZIP validation to Canadian addresses.