Geography reference

Counties and county equivalents

The unit almost every American dataset can be rolled up to, and the one most likely to be keyed by a five-digit code nobody labelled. Health, labour, agriculture and election data all land here.

The 58 counties of California, drawn from the exact boundaries Vizzie joins your data to — not a picture of them.

How the codes are built

Five digits: two for the state, three for the county. 06075 is San Francisco, 36061 is New York County. The same leading-zero trap as tracts applies and bites harder, because a five-digit code looks so much like a number — 01001 (Autauga County, Alabama) becomes 1001 and matches nothing.

"County equivalent" is doing real work in the name. Louisiana has parishes, Alaska has boroughs and census areas, Virginia has independent cities that sit outside any county, and Puerto Rico has municipios. They all carry county-shaped FIPS codes and all appear here.

What it rolls up into

1. Census tract — around 4,000 people
2. County or county equivalent
3. State

Which years exist

County boundaries are the most stable geography on this site — most have not moved in a century. The exceptions are worth knowing: Connecticut replaced its eight counties with nine planning regions for statistical purposes, which the Census Bureau adopted from 2022, so Connecticut data published either side of that line uses different codes for the same ground.

Vizzie holds the 2020 set, which is counties for Connecticut.

Map a spreadsheet of these

Paste a column of county codes into Vizzie with whatever you measured beside it. Vizzie recognises the code format, joins it to the boundaries above and draws the map — no shapefile, no download, no GIS install.

Open Vizzie

Boundaries: U.S. Census Bureau, 2020 Census — cartographic boundary files (public domain).
Licence: US-Census-Public-Domain. Source: US Census Bureau. Boundary counts and sizes measured from the data Vizzie holds, 2026-09-19.