On July 1, 1963, the United States Postal Service (USPS) introduces the Zone Improvement Plan as part of a plan to improve the speed of mail delivery, inaugurating the use of machine-readable ZIP codes to facilitate the efficient sorting of mail at a national level.
The idea wasn’t totally new. In 1943, the Post Office had created numbered zones for more than 100 urban areas around the country. But in the post-WWII boom, that system quickly became inadequate. Between 1943 and 1962, annual mail volume doubled from 33 billion to 66.5 billion pieces, and the average mailed letter passed through an average of 17 sorting stops. Suburbs were sprouting exponentially, and mail transport was shifting from railway to highway and air, making old urban hub systems obsolete.
