U.S. POSTAL CODE DIRECTORY

Every U.S. ZIP Code.
One simple search.

Find ZIP Codes by city, state, county, or number. Explore location details with a clean, easy-to-use directory.

✓ Browse by state✓ Search cities & counties✓ Explore ZIP+4 information
Directory coverage 42,735 ZIP Code records
ZIP Code Basics

What Is a U.S. ZIP Code? A Complete Beginner’s Guide

U.S. ZIP Codes Guide · Updated November 2026

A ZIP Code is a five-digit postal code used by the United States Postal Service (USPS) to help sort and deliver mail. ZIP is short for Zone Improvement Plan. The system was introduced in 1963 to make mail processing more efficient as the volume of mail grew.

The digits identify progressively smaller geographic areas in the mail network, but they are not a perfect map of neighborhoods or municipal boundaries. A ZIP Code can cover part of a city, several communities, or a delivery area organized around a post office. Use a current address lookup when accuracy matters.

For address-specific mailing decisions, verify the complete delivery address with the United States Postal Service (USPS). This directory is provided as a general reference.

← Back to all blog articles

ZIP codes are a system of postal codes used by the United States Postal Service (USPS) since 1963. The term ZIP, an acronym for Zone Improvement Plan, is properly written in capital letters and was chosen to suggest that the mail travels more efficiently, and therefore more quickly, when senders use the code in the postal address. The basic format consists of five decimal numerical digits. An extended ZIP+4 code, introduced in the 1980s, includes the five digits of the ZIP code, a hyphen, and four more digits that determine a more precise location than the ZIP code alone. The term ZIP code was originally registered as a servicemark (a type of trademark) by the U.S. Postal Service, but its registration has since expired.

ZIP codes designate only delivery points within the United States and its dependencies, as well as locations of its armed forces. There are no ZIP codes reserved for designating mail bound for foreign destinations (with the exception of U.S. military units stationed outside of the United States), and therefore, international outbound mail should not include a ZIP code in the delivery address. The last line of a foreign address must only show the name of the country of destination.

Useful Websites: US Zip Codes