A ZIP Code (an acronym for Zone Improvement Plan[1]) is a system of postal codes used by the United States Postal Service (USPS). The term ZIP was chosen to suggest that the mail travels more efficiently and quickly[2] (zipping along) when senders use the code in the postal address. The Philippine Postal Corporation also uses this terminology for the postal code system in the Philippines.[3]
Introduced on July 1, 1963, the basic format comprised five digits.[4] In 1983, an extended code was introduced named ZIP+4; it included the five digits of the ZIP Code, followed by a hyphen and four digits that designated a more specific location.
ZIP Code and ZIP+4 are registered trademarks of the United States Postal Service, which also registered ZIP Code as a service mark until 1997.[5]
When Day unveiled the nationwide 5-digit ZIP Code at a postmasters' convention in October of 1962, he simultaneously introduced the world to "Mr. ZIP" — the cartoon character whose body language symbolizes speedy delivery.