what are the last four digits in a zip code
ZIP Code For Post Office Boxes, the general (but not invariable) rule is that each box has its own ZIP+4 code. The add-on code is often one of the following: the last four digits of the box number (e.g. PO Box 107050, Albany, NY 12201-7050), zero plus the last three digits of the box number (e.g., PO Box 17727, Eagle River, AK 99577-0727), or, if the box number consists of fewer than four digits, enough zeros are attached to the front of the box number to produce a four-digit number (e.g., PO Box 77, Juneau, AK 99750-0077). However, there is no uniform rule, so the ZIP+4 Code must be looked up individually for each box.[citation needed]
List of U.S. state abbreviations 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.[12]