Add Yahoo as a preferred source to see more of our stories on Google. Most Americans know their ZIP code by heart. They type it into online forms, scribble it on envelopes and memorize it as part of ...

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.

The familiar five-digit number was part of a nationwide effort to modernize the mail.