ZIPs and FIPS: Codes You May Need – And Why

Get up to speed on FIPS Codes and ZIP Codes.

9 minute read

We tend to think of ZIP codes as geographic markers. They are–sort of. Having only the ZIP code for a building can give you a general idea of where it is located in the United States. We know that lower-numbered ZIP codes are associated with locations in the eastern part of the country, with numbers generally getting larger to the west. 

But we also know that ZIP codes cover a large area and can cross state boundaries. They aren’t reliable geographic position indicators. The reason is the US Postal Service developed ZIP codes to align with postal delivery routes. Using ZIP codes for any reason other than postal delivery can be misleading. The results may not be what you expect. 

County-Level Precision

What if you needed to know the county in which a person resides? If the only information you had was the person’s ZIP code, you’d be in trouble. ZIP codes have nothing to do with the lines that define a county. One ZIP code could include addresses in multiple counties and a single county might include hundreds of ZIPs!  

If the county is an important data point for you, there’s another way to go. The Federal Information Processing Series (FIPS) is a set of 5-digit codes that designate every county (or similar jurisdiction) in every US state. The government developed FIPS codes to assure smooth data exchanges across technical communities, contractors, and government agencies and for data security purposes. 

Many national government agencies, including the US Census Bureau, US Health and Human Services, and the National Weather Service, use FIPS codes. Local government also uses the codes for applications such as sales and use tax calculations and public health. 

Reduce Errors

FIPS codes are better values to store in databases than county names. People can misspell county names, causing inconsistent or incorrect matching. Consider Sainte Genevieve County, Missouri. One can easily see this county name recorded as Saint Genevieve, Ste. Genevieve, or St. Genevieve. Common county names could cause problems as well. Thirty-one states have a county named “Washington” for example. Matching on a consistent five-digit number is more reliable. 

Another good quality of FIPS codes is they rarely change. ZIP+4 codes, by comparison, do change frequently as the US Postal Service modifies their delivery networks, new homes are built, or post offices are relocated.

Organizations that must make business decisions based on the county in which an address is located need to add the FIPS codes to their databases. FIPS codes determined from postal addresses are consistently accurate. If your company needs to add FIPS as a data element, you’ve got to first ensure your postal addresses are accurate and standardized. That’s the job of Firstlogic’s Address IQ® software. Address IQ, formerly known as Firstlogic ACE®, cleanses your address data by checking against the authoritative USPS® CASS™ database. The software adds ZIP+4 codes and references resources such as DPV®, LACSLink®, USPS® NCOALink®, and SuiteLink® to ensure the addresses in your database are current and correct. Address IQ is also capable of appending the five-digit FIPS codes discussed in this article. 

Uses for FIPS Codes

Once your data includes FIPS codes, you can accurately determine the county in which an address is located. Many applications rely on this information to assess taxes, administer elections, distribute benefits such as food stamps, disseminate public information, select residents for jury duty, and more. 

Commercial applications can also take advantage of the unique geolocation data that FIPS codes offer. Many times, a precise location determined by latitude and longitude is unnecessary for simple tasks, such as segmenting a mailing list. Knowing the county of residence is enough information to ensure you don’t distribute communications pertinent to one county to residents of a neighboring county. 

Any organization that accesses county-level government information, such as weather data, can connect to those government sources easily via FIPS codes. Property insurance premiums, for instance, often depend on the chance for weather-caused damage such as hail, high winds, or flooding. Weather patterns can vary by county, so referencing location-based weather information from the National Weather Service helps insurers compute the cost and deductible figures for property insurance policies. 

What’s in the Codes?

The first two digits of a FIPS code designate the state in which each county is located. The government assigned the codes sequentially, starting with 01 for Alabama, 02 for Alaska, etc. Remaining codes were assigned to the states alphabetically, with a few gaps left to allow for any possible new states to be added to the union, such as American Samoa or Guam. 

The last three digits of FIPS codes correspond to a county. These digits are also assigned via an alphabetical list of counties within a state. The first alphabetical county in a state receives code 001, the second will be assigned 003, etc. Only odd numbers are used, leaving room for expansion should new counties be added at a later date. 

ZIP codes are great for postal delivery. They can even be useful when a precise physical location is unnecessary, such as locating all the furniture stores within a ZIP code. But to identify counties across the US, add FIPS codes to your corporate name and address databases. Firstlogic’s Address IQ software ensures your postal addresses are current and correct and then adds the FIPS codes for you. With FIPS codes on file, your organization can easily connect with government information sources that provide a wealth of information necessary for decision-making and analysis. 


See below for a list of state-level FIPS codes in use by organizations nationwide.  

State Postal Abbr. FIPS Code State Postal Abbr. FIPS Code 
Alabama AL 01 Nebraska NE 31 
Alaska AK 02 Nevada NV 32 
Arizona AZ 04 New Hampshire NH 33 
Arkansas AR 05 New Jersey NJ 34 
California CA 06 New Mexico NM 35 
Colorado CO 08 New York NY 36 
Connecticut CT 09 North Carolina NC 37 
Delaware DE 10 North Dakota ND 38 
District of Columbia DC 11 Ohio OH 39 
Florida FL 12 Oklahoma OK 40 
Georgia GA 13 Oregon OR 41 
Hawaii HI 15 Pennsylvania PA 42 
Idaho ID 16 Puerto Rico PR 72 
Illinois IL 17 Rhode Island RI 44 
Indiana IN 18 South Carolina SC 45 
Iowa IA 19 South Dakota SD 46 
Kansas KS 20 Tennessee TN 47 
Kentucky KY 21 Texas TX 48 
Louisiana LA 22 Utah UT 49 
Maine ME 23 Vermont VT 50 
Maryland MD 24 Virginia VA 51 
Massachusetts MA 25 Virgin Islands VI 78 
Michigan MI 26 Washington WA 53 
Minnesota MN 27 West Virginia WV 54 
Mississippi MS 28 Wisconsin WI 55 
Missouri MO 29 Wyoming WY 56 
Montana MT 30