What is the National ZIP+4 Address Database?#

“The National ZIP+4 Address Database consists of 929 separate address files in fixed-length ASCII format, organized by 3-digit ZIP code. Each file contains a variable number of fixed-field-length ASCII ZIP+4 (9-digit ZIP code) address records of 182 bytes each, with no record delimiter (no carriage return nor line feed characters). Within a given file, the records are sorted by 5-digit ZIP code. Each file is compressed as a zip archive (WinZip).

This database also includes the US Postal Service city-state file, which contains a complete listing of the approximately 42,500 5-digit ZIP codes currently assigned by the USPS. This file has approximately 77,800 fixed-field-length ASCII records of 129 bytes each. This file is also compressed as a zip archive (WinZip).”

How often is National ZIP+4 Address Database updated?#


What data source(s) does National ZIP+4 Address Database use?#

“USPS City-State file (42,500 5-digit ZIP Codes currently assigned by USPS ZIP+4 Address Files USPS Address Information Products Technical Guide”

Where can I find the product release notes?#


Where can I find the product documentation?#


Where can I find information to automate updates?#



What is the City State file?#

The CITY STATE (“ctystate.txt”) file is a comprehensive list of 5-digit ZIP Codes and the city, county, and post office names associated with those ZIP Codes.

What is the City State file used for?#

It is used to validate city names and ZIP Codes used as part of a mailing address, and as a link to other Address Information Systems products.

How is the file sorted?#

The file is sorted according to the ASCII collating sequence, in ascending order, on the data fields, ZIP CODE and UPDATE KEY NO.

How is this product sorted?#

Each file is sorted by 5-digit ZIP Code.