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

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.

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 ...

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 ...

We all have one, we know it by heart, and we share it with our neighbors. But chances are you haven't thought that much about this ubiquitous part of American life — the ZIP code. We all know about ...