ZIP is the acronym for Zoning Improvement Plan.
What is Zoning Improvement Plan?
Before the 1960s, mail was delivered based on the city and state it was addressed to, plus a two-digit postal code that indicated a broad region. In 1962, the United States Postal Service expanded this system to what we know as modern zip codes to assist in mail sorting and make it easier and faster to get an ever-increasing amount of mail to where it needed to go. The acronym Zip was chosen specifically to indicate that letters and packages arrive faster––zippier, if you will––when zip codes are used. Zip codes expanded to 5 digits and then to 9 digits for more precision in the United States.