What ZIP Codes Mean: How to Decipher Postal Codes

Learn the information that each digit in a ZIP Code corresponds to and how USPS uses postal codes to determine crucial address information
what ZIP codes mean
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Have you ever wondered what all the numbers in a ZIP Code mean? From the sorting process to final delivery, the meaning behind each digit in ZIP Codes (also known as “postal codes”) allows USPS and its letter carriers to determine exactly where a letter or package is traveling to.

Breaking Down What Each Number in a Postal Code Means

The First Digit

Casting a “wider net,” if you will, the first number in a ZIP code designates a particular state of an address. These numbers start from 0 in the eastern part of the U.S. and go higher the further west you travel. For instance, postal codes in Maine all begin with a 0, while each postal code in California begins with a 9.

Here are all the states that the first digit of a postal code corresponds to:

  • 0: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, Rhode Island, Vermont
  • 1: Delaware, New York, Pennsylvania
  • 2: Maryland, North Carolina, South Carolina, Washington, D.C., West Virginia, Virginia
  • 3: Alabama, Florida, Georgia, Mississippi, Tennessee
  • 4: Indiana, Kentucky, Michigan, Ohio
  • 5: Iowa, Minnesota, Montana, North Dakota, South Dakota, Wisconsin
  • 6: Illinois, Kansas, Missouri, Nebraska
  • 7: Arkansas, Louisiana, Oklahoma, Texas
  • 8: Arizona, Colorado, Idaho, Nevada, New Mexico, Utah, Wyoming
  • 9: Alaska, California, Hawaii, Oregon, Washington

The Second Digit

After the first number, the next two digits in a postal code reflect the code USPS has designated for one of its larger regional facilities, such as a sorting hub or distribution center.

The Last Two Digits

Lastly, the final two digits of a postal code designate the local Post Office or distribution center closest to the final address.

What About the ZIP+4 Code?

The final four digits you sometimes see on ZIP Codes act as specific “coordinates” for addresses, if you’d like to think of them that way. USPS introduced these digits to the end of postal codes in 1983 to allow its systems to pinpoint exact delivery points. Every residential address in the U.S. has its own unique ZIP+4, and when USPS has a ZIP+4 code, they don’t even need any other parts of the address to know where a letter or package is heading!

To learn more about ZIP Codes and how they originated, check out our guide: Why Zip Codes Are So Important.

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