definition
strict definition
US county FIPS code
The three-digit code identifying a county within its state, published by the Census Bureau as INCITS 31 and still widely called a FIPS code.
Three digits, and unique only inside one state. Every state has a county 001, so the same three digits appear more than fifty times across the country and mean a different county each time. The code identifies a county only when the state is already known.
For a value that stands on its own, use the US county GEOID, which prefixes the state and is unique nationwide.
Counties are stable but not permanent. Connecticut replaced its eight counties with nine planning regions in 2022, and those carry new codes. Leading zeros are part of the code.
