County Data by Zip Code

Main Data Sources and Updates

USPS Database
Monthly Update

US Census TIGER
Database 2010-2025

Please contact us for your specific needs.

County District Data

Available products in the current market and their problems

There are "County by Zip Code" and "County by Census Block, Block Group and/or Tract" county data files. Following are common problems that our competitors have:

Available
in Current Market

Problems

"5 Digit Zip Code to County" District Data

Imprecise
5 digit zip codes cross county lines, sometimes straddling deep into two or more counties.
PO Boxes may serve more than one county.

"9 Digit Zip Code to County" District Data

Incomplete
Leaves out large regions in which mail is not delivered to residences. Holes in data make whole sections of counties disappear from the applications in which they are used.

"Census Block, Block Group and/or Tract to County" District Data

Census Block, Block Group, and Tracts are all designed by the US Census TIGER/Line team to not cross county lines. These entities are the basic building blocks of the TIGER/Line files and are used for all statistical analyses done by the Census Bureau. Census blocks and the block groups and tracts built from them are created and re-aligned with the decennial census.

Out-of-Date
Census block files do not stay current with newly created addresses. The 2020 US Census Blocks are the most accurate yet produced by the US Government. However, on the day it was published, it was already be a year or more behind the additions to addresses and changes in US Postal Service zip code assignments. As good as they are for demographic analysis and Census reports of demographic trends, they contain no zip+4 or carrier route information and cannot be used reliably for directing mail campaigns or targeting mailings to the census block or tract level.

USgeocoder Solutions

100% accuracy for existing addresses, 99% accuracy for new addresses

Using its proprietary algorithms, USgeocoder combines US Census block data and US Postal Service addressing data to assign new addresses to census block, block group, census tract, zip+4, and carrier route to the entire country and its possessions. USgeocoder can assign these addresses with 99% accuracy.

Most frequently updated data you can find

USgeocoder is installed with 2025 Census TIGER data.

Every month, USgeocoder uses US Postal Service data to update the TIGER/Line census files. Typically, a new address is available to USgeocoder within thirty days after the US Postal Services' first delivery to it.

Here is the sample header of "County by Zip Code" data files.

Zip 5

Zip 4

County

USgeocoder also offers "Address Range-To-County" for better accuracy. Here is the sample header of "Address Range-To-County" data files.

Address Low

Address High

County

We can produce custom data files per your specifications. Files are available annually, semi-annually, quarterly, or monthly. They may be purchased by state, region, or the whole country. Please contact us for flexible options and pricing details.

You can use USgeocoder data files in many ways:

- Use our data files in your own GIS applications or demographic analysis software
- Let us batch process your address data for district matching
- Get REAL TIME information for your address via USgeocoder API
- Display and explore your data with USgeocoder's GIS mapping engine

USgeocoder also provides demographic services and custom GIS application development.
Contact us to see how we can help.