Zonal Improvement Plan (ZIP) code system, introduced to improve sorting and delivery of mail, has been around for more than 65 years. A ZIP code identifies a specific geographic mail delivery area, which makes it convenient to deliver the mail on the correct address.

In 1943, the US Post Office Department adopted the postal zones for large cities, which were simply 1 or 2 digits representing the specific zone in the individual city. E.g., Minneapolis 16. The ZIP codes, as we know today, came into being in 1963 and owe their origin to an employee of the post office, Robert Moon. Resultantly, the existing codes for postal zones were preceded by 3 digits describing the Sectional Center Facility (SCF). An SCF that is assigned the first 3 digits sorts the mail for the postal zone described by the last 2 digits. E.g., Minnesota 23716 (237 depicts SCF Number and 16 depicts the Postal Zone).

To further pinpoint the accuracy of the address on the mail, Zip + 4 system was adopted in 1983, which uses the ZIP code plus 4 additional digits to identify a geographic segment within the ZIP code delivery area (like apartments, city blocks etc.). E.g. CA 95823-5429.

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