ZIP Code
numeric postal code used in the United States and its territories
The ZIP Code system (an acronym for Zone Improvement Plan) is the 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 (zipping along) when senders include the code in the postal address. ZIP+4 is a registered trademark of the United States Postal Service, which also registered ZIP Code as a service mark until 1997, and which claims "ZIP Code" as a trademark though it is not registered.
Introduced on July 1, 1963, the basic format was five digits, the first designating a region of the country and subsequent digits localizing the destination further. 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 location even more specific than the original five.
Private carriers and the USPS use ZIP Codes to route deliveries. In addition, ZIP Codes have become a basis for breaking down demographic, marketing, and sales data for analytical purposes.
History
Early postal zones
The early history and context of postal codes began with postal district/zone numbers. The United States Post Office Department (USPOD) implemented postal zones for 124 large cities in May 1943. Postmaster General Frank C. Walker explained that many experienced postal clerks were going into the army, and the zone system would enable inexperienced clerks to sort mail without having to learn the delivery area of each city carrier.
“ZIP Code” enters the record as numeric postal code used in the United States and its territories. Crown Archives preserves that source wording while asking what Code, numeric and postal can confirm, complicate or overturn.
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“ZIP Code” is worth following because a concise public description often conceals a longer documentary argument. Here, Code, numeric and postal provides the most credible route into that argument.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Sep 23, 2026. The linked authority identifier is Q136208. The Library of Congress control number is sh99004092. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1997, 1963, 1983 and 1943.
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This entry incorporates text from “ZIP Code” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.