ZIP codes were introduced in 1963 to make the mail delivery process quicker and more efficient. Tony Anderson via Getty Images Most Americans know their ZIP code by heart. They type it into online ...

Back in the 1960s, there was a heaping surplus of mail in the U.S. Post offices were struggling to keep up with deliveries. According to the Smithsonian's National Postal Museum, mail volume reached ...

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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.