History of ZIP Code - US Postal Service

US Postal Service ZIP Code SystemZIP stands for Zoning Improvement Plan which began on July 1, 1963 as a solution to the explosive growth of business mail. The Post Office didn't require anyone to use the new ZIP Code system at the beginning, but in 1967, the Post Office required mailers of second-class and third-class mail to presort by ZIP Code.

For a complete history of ZIP Code system, please refer to the ZIP Code section of the History of the United States Postal Service 1775-1993 web page.