State/Province Code
A standardized abbreviation identifying a state, territory, or province within a country's mailing address system.
In the United States, the USPS uses 2-letter state abbreviations (CA for California, NY for New York) established in 1963 alongside the ZIP code system. These abbreviations cover the 50 states, the District of Columbia (DC), and U.S. territories including Puerto Rico (PR), Guam (GU), American Samoa (AS), and the U.S. Virgin Islands (VI). Military addresses use pseudo-state codes AA, AE, and AP.
Canada uses 2-letter provincial and territorial abbreviations (ON for Ontario, BC for British Columbia). Other countries have their own conventions: Australia uses state abbreviations like NSW and VIC, while many European countries omit the state/province entirely, relying solely on the postal code.
Using the correct state code is critical for automated mail processing. OCR equipment reads the last line of an address as a unit, and an incorrect state code can cause misrouting.