When ZIP codes started

Updated: March 3, 2026

The question when ZIP codes started refers to the origin of the United States ZIP code system. ZIP codes were introduced by the United States Postal Service in 1963.

Before ZIP codes, mail sorting relied heavily on city names and manual routing. As mail volume increased, USPS needed a more efficient system. ZIP codes were created to improve sorting speed and accuracy.

The original ZIP code consisted of five digits. The first digit represented a broad region, while the remaining digits refined the delivery area. In 1983, USPS introduced ZIP+4 to further improve precision.

ZIP codes were initially optional but gradually became standard as businesses and individuals recognized their benefits.

Understanding when ZIP codes started helps explain their design limitations. ZIP codes were built for mail routing, not geographic analysis, which is why they do not always align with city or county boundaries.

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