What a ZIP Code means
ZIP Code stands for Zone Improvement Plan Code. The United States Postal Service introduced the five-digit system in 1963 to make mail sorting and delivery more efficient as mail volumes grew. A ZIP Code is a routing aid: it helps direct mail through the postal network toward a delivery area.
How the five digits work
The first digit identifies a broad geographic area of the country, while the following digits narrow the routing geography. The digits should be treated as a postal routing identifier, not as a precise map coordinate or a guarantee that every address in a city shares the same ZIP Code.
ZIP Codes and local place names
A single city may use several ZIP Codes, and a ZIP Code may be associated with a preferred city name that differs from a municipality’s official name. For a specific mailing, use the complete address and verify it with USPS rather than relying only on a city-level search.
When to look up a ZIP Code
A ZIP Code lookup can help complete an address, organize a mailing list or understand a location record. For delivery decisions, confirm the address and ZIP+4 information through official postal tools.