On July 1, 1963, the U.S. Post Office Department introduced the ZIP code program to get a handle on the heaping surplus of mail. Today, those five digits represent much more for American society. Back ...

Most Americans know their ZIP code by heart. They type it into online forms, scribble it on envelopes and memorize it as part of their address. But not everyone knows the original meaning of the term.

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Everyone knows the ZIP code 90210—but what about these other notable codes around the country? The Zone Improvement Plan, otherwise known as the ZIP code, is the network of postal codes the U.S.