What is a ZIP code? Structure, examples and meanings

If you are customer of United States Postal Service (USPS) or other delivery service (FedEx, United Parcel Service, DHL, etc), you will most likely need to know your ZIP code. What it means, we will tell you in this article.

Outside USA the system of ZIP-codes isn’t used. The only country where it is the standard term is the Philippines. Most countries in the world use the term Postcode, Postal index or some other.

What is a ZIP code?

A ZIP Code is a postal code which is used by the USPS (United States Postal Service). ZIP codes appeared in the 1960s as a necessary measure for faster sorting of mail and faster delivery.

ZIP abbreviation means “Zone Improvement Plan”.

How many digits are in ZIP code?

Firstly, ZIP codes consisted of 5 digits, but in the 1980s they were expanded to nine digits, so that ZIP codes looked like combination divided with a hyphen — XXXXX-YYYY. For example: 01234-5678.

ZIP codes format

ZIP code 5 plus 4 meaning is the same but it provides an opportunity to designate a more specific location.

Nowadays the following ZIP code formats are valid:

  • 5-digit ZIP codes;
  • 5-digit ZIP codes + 4 additional digits.

The additional 4 digits represent the local geographic segment within the 5-digit delivery area. They allow you to specify the delivery address, however, thanks to modern technologies a 5-digit code is still enough for delivery.

ZIP code structure

ZIP Codes are numbered in such a way so that they have the following structure:

  • The first digit is an identifier of certain U.S. states group.
  • The second and third digits together represent a region in that group (or a large city in some cases).
  • The fourth and fifth digits are numbers of a group of delivery addresses within that region.

The first three digits usually mean a sectional center facility, the mail sorting and distribution center for an area, although a sectional center facility may have longer identifier than one three-digit code.

At the same time, by the first digit, it is possible to determine the geographic location of delivery zone:

First digit of ZIP code Its geographic location
“0”, 0XXXX Connecticut (CT), Massachusetts (MA), Maine (ME), New Hampshire (NH), New Jersey (NJ), New York (NY, Fishers Island only), Puerto Rico (PR), Rhode Island (RI), Vermont (VT), Virgin Islands (VI)
“1”, 1XXXX Delaware (DE), New York (NY), Pennsylvania (PA)
“2”, 2XXXX District of Columbia (DC), Maryland (MD), North Carolina (NC), South Carolina (SC), Virginia (VA), West Virginia (WV)
“3”, 3XXXX Alabama (AL), Florida (FL), Georgia (GA), Mississippi (MS), Tennessee (TN)
“4”, 4XXXX Indiana (IN), Kentucky (KY), Michigan (MI), Ohio (OH)
“5”, 5XXXX Iowa (IA), Minnesota (MN), Montana (MT), North Dakota (ND), South Dakota (SD), Wisconsin (WI)
“6”, 6XXXX Illinois (IL), Kansas (KS), Missouri (MO), Nebraska (NE)
“7”, 7XXXX Arkansas (AR), Louisiana (LA), Oklahoma (OK), Texas (TX)
“8”, 8XXXX Arizona (AZ), Colorado (CO), Idaho (ID), New Mexico (NM), Nevada (NV), Utah (UT), Wyoming (WY)
“9”, 9XXXX Alaska (AK), American Samoa (AS), California (CA), Guam (GU), Hawaii (HI), Marshall Islands (MH), Federated States of Micronesia (FM), Northern Mariana Islands (MP), Oregon (OR), Palau (PW), Washington (WA)

 

Examples of ZIP codes

There are four types of ZIP Codes:

  • Unique ZIP code belongs to a single high-volume address (governmental agencies, universities, businesses and other large objects). 20505 is example for ZIP code assigned to Central Intelligence Agency in Washington. 21252 is example of ZIP code, which belongs to Towson University.
  • Post office box-only ZIP codes are used only for PO boxes at a given facility, not for any other type of delivery.
  • Military ZIP codes are necessary for mail routing to the U.S. military
  • Standard ZIP Codes are usual postal codes.

What’s my ZIP code?

To know your full ZIP-code you can use free service “Look Up a ZIP Code”. It can be found on our site as well as on USPS.com. All you need is to search correct ZIP code by your city and state.

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