What Is a FIPS Code? A Plain-English Explainer

If you've ever opened a Census Bureau spreadsheet, a Bureau of Labor Statistics file, or an EPA dataset and wondered what those 2- or 5-digit numbers in the geography column mean, you've encountered FIPS codes. FIPS stands for Federal Information Processing Standards, and the geographic variant — formally called ANSI codes since 2008 — are the universal identifiers that link state, county, and metropolitan area data across every major federal agency.

A state FIPS code is a 2-digit number assigned to each US state and territory. California is 06, Texas is 48, Washington is 53. A county FIPS code is 5 digits: the 2-digit state code followed by a 3-digit county code. King County, Washington is 53033 — state 53 (Washington) plus county 033. This simple structure makes it trivially easy to join datasets from different agencies without any string matching or geocoding.

The power of FIPS codes lies in their universality. When the Census Bureau publishes population estimates, the BLS publishes unemployment rates, and the EPA publishes air quality data, they all use the same county FIPS codes. A single join key unlocks every dataset. That's why data professionals working with government data treat FIPS fluency as a baseline skill.

Beyond states and counties, FIPS codes extend to Metropolitan Statistical Areas, Congressional Districts, Census tracts, block groups, and individual blocks — each level nesting cleanly inside the one above. Our complete guide to FIPS codes covers the full hierarchy. To look up any code, use the search tool or browse directly by state.