Census Geography Hierarchy
The official nesting of block groups, tracts, counties and states that gives every small area its place in the national hierarchy.
Census statistical geography nests: block groups sit inside census tracts, tracts inside counties, counties inside states. This record holds that hierarchy as the Census Bureau publishes it — one entry per block group, with the tract, county and state it belongs to, and the Bureau's official name for each.
It contains identifiers and names only. No survey estimates are held under this record.
Coverage#
The hierarchy is taken from the 2020-2024 American Community Survey 5-year release, covering the 50 states and the District of Columbia. The Bureau's guidance on geography boundaries by year is that a 5-year release uses the last year of its period to determine geographic vintage, and for the 2024 estimate year both census tracts and block groups are of 2020 Census vintage. Counties and other legal areas can change between annual releases.
The identifier for this record retains an older name referring to 2020 redistricting files. The hierarchy in use is the one described above, from the Census API.
How we use it#
This is the backbone that tells us which county a tract belongs to and what that county is officially called. Many of the datasets Birdseye reports are published for counties rather than tracts, and this hierarchy is what connects the two. It is also the source of the canonical county list used throughout the tool.
It produces no metric of its own.
Considerations#
The hierarchy describes statistical geography as of a single release. Areas whose boundaries or names changed after that release will reflect the older definition until the next refresh.
Citation#
U.S. Census Bureau, American Community Survey 5-year estimates geography (2020-2024), accessed via the Census Bureau Data API.
This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau. Per Census Bureau citation policy, the Bureau is cited as the source of the original data only.
References#
- 1US Census Bureauhttps://www.census.gov/data/developers/data-sets/acs-5year.html
- 2Geography Boundaries by Yearhttps://www.census.gov/programs-surveys/acs/geography-acs/geography-boundaries-by-year.html
- 3Census Bureau citation policyhttps://www.census.gov/about/policies/citation.html