<P> 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 . </P>
<P> 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 . </P>
when did state abbreviations change to two letters
when did state abbreviations change to two letters
October 1963
October 1963