What does ZIP stand for in postal ZIP codes?

Question: What does ZIP stand for in postal ZIP codes?

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Zone Improvement Plan.

ZIP in postal ZIP codes is an acronym that stands for “Zone Improvement Plan.” The United States Postal Service (USPS) introduced the ZIP code system in 1963 with the aim of improving efficiency and accuracy in mail delivery.

Before this system, mail in the United States was sorted by hand based on local addresses, which was a time-consuming and error-prone process, especially with the growth of cities and towns. The introduction of ZIP codes meant that mail could be sorted mechanically, speeding up the process and reducing mistakes.

A ZIP code is a five-digit number. The first digit represents a broad geographical area of the United States, ranging from 0 for the Northeast to 9 for the West. The next two digits specify a regional area within that group, and the last two digits designate a specific post office or delivery area.

In 1983, USPS introduced the ZIP+4 code, which added a hyphen and four extra digits to the end of the ZIP code to allow for more precise sorting – down to a city block, a group of apartments, or an individual high-volume receiver of mail.