List of U.S. state and territory abbreviations
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 made for five outlying territories; all are the same as the USPS abbreviations except the Mariana Islands. The twelve cases where USPS and USCG abbreviations are different are listed below and marked in bold red in the table above; they include three inland states with a small Coast Guard group. These twelve abbreviations were changed to avoid conflicting with the ISO 3166 two-digit country codes.