ACS 5-Year Estimates: Accessing Census Data by FIPS Code

The American Community Survey (ACS) 5-year estimates are the most widely used source of small-area demographic, economic, and housing data in the US. Published annually for every Census geography down to the block group level, the 5-year estimates aggregate survey responses over a 5-year period to produce reliable estimates even for small populations. All ACS geographies are identified by FIPS codes and GEOIDs, making them directly joinable to any other federal dataset.

The Census Bureau's Data API is the most efficient way to access ACS data programmatically. A typical request URL: https://api.census.gov/data/2022/acs/acs5?get=NAME,B01003_001E&for=county:*&in=state:53 returns population estimates for all counties in Washington state (FIPS 53). The state:53 and county:* parameters use FIPS codes. For a specific county like King County, use county:033&in=state:53.

ACS variables are organized into tables: B-tables are base tables (full detail), C-tables are collapsed versions, S-tables are subject tables, and DP-tables are data profiles. The variable B01003_001E is total population; B19013_001E is median household income; B15003_022E is bachelor's degree attainment. The Census Bureau's variables API (/variables.json) documents all available variables for each dataset and year.

When working with ACS data, keep vintage in mind. The 2022 5-year ACS (covering 2018–2022) uses 2020 Census boundaries. Older vintages used 2010 boundaries. County FIPS codes are stable, but Census tract boundaries change after each decennial. For county-level analysis, this doesn't matter — just ensure you're using the right 5-digit FIPS code from the county codes reference. Our federal data guide covers the ACS alongside other major Census products.