A ZIP code number is a five-digit postal code assigned to an area in the United States or its overseas military stations. ZIP is an acronym for Zone Improvement Plan.
ZIP codes were created by the United States Postal Service in 1963 to assist with the sorting of mail. These numbers can be used for a single address that receives high volumes of mail, such as a university, or they can be used for cities or regions. The first digit of the ZIP code represents a specific group of states, moving east to west; "0" represents eastern states and "9" represents western states. There are more than 40,000 ZIP codes in the United States.