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.

Today marks the 50th anniversary of the Zone Improvement Plan, the network of ZIP codes we use for everything from mail delivery to credit card security. The U.S. Postal Service began using the ...

For some credit card purchases in Canada, a postal code is required as a security measure. If using a credit card in the U.S., you may need to use a ZIP code instead. Use the postal code from the ...