FIPS Codes in Federal Datasets

FIPS codes are the universal geographic key in US federal data. Nearly every agency that publishes geographic statistics uses them. If you're joining two federal datasets by location, you're almost certainly joining on FIPS codes.

Census Bureau

The Census Bureau originated the FIPS standard and uses it everywhere:

American Community Survey (ACS) — 5-digit county FIPS and 2-digit state FIPS in all data files. The GEOID column in Census downloads is always a FIPS code.
Decennial Census — P.L. 94-171 redistricting files use FIPS at every geographic level from state down to block.
Population Estimates Program — County-level population estimates keyed by 5-digit FIPS.
TIGER/Line Shapefiles — GIS boundary files indexed by FIPS codes. The STATEFP and COUNTYFP columns are standard FIPS components.
data.census.gov — All geographic filters use FIPS codes internally.

Bureau of Labor Statistics (BLS)

Quarterly Census of Employment and Wages (QCEW) — County- and state-level employment data uses 5-digit FIPS as the area identifier.
Occupational Employment and Wage Statistics (OEWS) — Uses MSA FIPS codes (5-digit) and state FIPS for geographic area files.
Local Area Unemployment Statistics (LAUS) — State and county FIPS codes used throughout.
Consumer Expenditure Survey — Geographic identifiers derived from FIPS codes.

Environmental Protection Agency (EPA)

Air Quality System (AQS) — Monitor locations identified by state + county FIPS.
Toxics Release Inventory (TRI) — Facility locations include county FIPS.
Superfund (CERCLIS) — Site data includes county FIPS.
Water Quality Portal — Uses FIPS for state and county-level aggregation.
EnviroAtlas — Ecosystem service indicators aggregated at the county FIPS level.

Department of Housing and Urban Development (HUD)

Fair Market Rents (FMR) — Published by county FIPS and MSA FIPS. HUD uses 5-digit county FIPS as primary keys in all downloadable files.
Comprehensive Housing Affordability Strategy (CHAS) — Income and housing burden data keyed to county FIPS.
Low Income Housing Tax Credits (LIHTC) — Project-level data includes county FIPS.
Point-in-Time Homeless Count — Continuum of Care (CoC) areas mapped to county FIPS.

USDA (Agriculture)

Economic Research Service (ERS) — Rural-urban continuum codes, county typology codes, and economic indicators all keyed by 5-digit county FIPS.
National Agricultural Statistics Service (NASS) — Census of Agriculture data uses county FIPS.
Farm Service Agency — Farm loan and payment data uses county FIPS.

Bureau of Economic Analysis (BEA)

GDP by County — Real GDP by county uses 5-digit FIPS.
Personal Income by County — Per-capita income, employment, earnings all keyed by county FIPS.
GDP by Metro Area — Uses MSA FIPS codes.

Centers for Disease Control (CDC)

CDC WONDER — Mortality and natality data downloadable by state and county FIPS.
500 Cities / PLACES — City and county-level health indicators using FIPS.
BRFSS — Behavioral Risk Factor Surveillance System uses state FIPS codes.

Centers for Medicare & Medicaid Services (CMS)

Medicare Enrollment Dashboard — County-level beneficiary counts by FIPS.
Provider of Services File — Hospital and provider data includes county FIPS.
Chronic Conditions Data Warehouse — Aggregated by county FIPS.

Practical Tips for Working With FIPS Codes

Always store FIPS codes as strings, not integers. Leading zeros are significant — 01001 is Autauga County, AL, not 1001. Storing as an integer strips the leading zero and breaks all joins.

Zero-pad to the correct length. State codes should always be 2 characters, county codes 5 characters. Use LPAD(fips, 5, '0') in SQL or str.zfill(5) in Python if your source data dropped leading zeros.

MSA vs county FIPS are different namespaces. An MSA code like 42660 (Seattle) is not a county code even though it's also 5 digits. They're maintained in separate reference files and come from different sequences.