The ACS typically publishes estimates using the latest available geographic boundaries (also known as "vintages"). For ACS 5-year estimates, use the last year of the estimate period to determine the vintage. For example, the following datasets use the same vintages of geographic boundaries:

2021 ACS 1-year estimates
2017-2021 ACS 5-year estimates

To learn more about geographic concepts used in the ACS, check out our geographic handbook Geography and the American Community Survey: What Data Users Need to Know.

2021

Legal Areas
Statistical Areas

Legal Areas

Legally defined geographic areas used in the ACS are updated on an annual basis from a variety of programs, including: the Boundary and Annexation Survey (BAS), the Redistricting Data Program and the School District Review Program.

Summary Level	Geographic Area	Vintage of Geographic Area for 2021 ACS Estimate Year
040	State and State Equivalent	January 1, 2021
050	County or equivalent (Alaska boroughs, Louisiana parishes, Puerto Rico municipios, independent cities)	January 1, 2021
County Subdivision
067	Township, Minor Civil Division (MCD)/Barrio and Barrio-Pueblo	January 1, 2021
Place
160	Incorporated Place	January 1, 2021
American Indian/Alaska Native/Hawaiian Home Land
230	Alaska Native Regional Corporations (ANRCs)	2020 Census
250/252/254	Federal American Indian Reservation (federal AIR)	January 1, 2021
250/252	State American Indian Reservation (state AIR)	2020 Census
251	American Indian Tribal Subdivision, federal AIR	January 1, 2021
250/254	Hawaiian Home Land (HHL)	2020 Census
Other Legal Areas
500	Congressional District, Delegate District DC, Resident Commissioner District PR	116th Congress of the United States^/4
610/620	State Legislative Districts (Upper and Lower Chambers)	2018 Legislative Session Year^/4
950/960/970	School District (Elementary, Secondary, Unified)	January 1, 2021
170	Consolidated City	January 1, 2021

Statistical Areas

For statistical areas, boundary changes are mostly associated with updates from each decennial census. Statistical areas are designed to have stable boundaries over time.

Summary Level	Geographic Area	Vintage of Geographic Area for 2020 ACS Estimate Year
050	County Equivalent (Census Areas in Alaska)	January 1, 2021
County Subdivision
060	Census County Division (CCD)	2020 Census^/1
Place
160	Census Designated Place (CDP)/Zona Urbana and Comunidad	2020 Census^/1
American Indian/Alaska Native/Hawaiian Home Land
250/252	Tribal Designated Statistical Area (TDSA)	2020 Census
250/252	State Designated Tribal Statistical Area (SDTSA)	2020 Census
250/252	Oklahoma Tribal Statistical Area (OTSA)	2020 Census
251	American Indian Tribal Subdivision (within OTSA)	2020 Census
256	Tribal Tract	2020 Census^/1
258	Tribal Block Group	2020 Census^/1
250/252	Alaska Native Village Statistical Area (ANVSA)	2020 Census
Other Statistical Areas
310	Metropolitan Statistical Area/Micropolitan Statistical Area	March 6, 2020^/3
312	Metropolitan Statistical Area/Micropolitan Statistical Area - Principal City	March 6, 2020^/2,/3
350	New England City and Town Area (NECTA)	March 6, 2020
352	New England City and Town Area - Principal City	March 6, 2020^/2
400	Urban Area	2010 Census^/4
140	Census Tract	2020 Census^/1
150	Census Block Group	2020 Census^/1
795	Public Use Microdata Area (PUMA)	2010 Census^/4
860	5-digit ZIP Code Tabulation Area (ZCTA)	2020 Census

^/1Changes to the boundaries of legal areas may cause complementary changes to the boundaries of selected statistical areas.

^/2While the American Community Survey (ACS) data generally reflect the Office of Management and Budget (OMB) definitions of metropolitan and micropolitan statistical areas; in certain instances the names, codes, and boundaries of the principal cities shown in ACS tables may differ from the OMB definitions due to differences in the effective dates of the geographic entities.

^/3The Census Bureau is planning on publishing the updated boundaries for this geographic summary level with the 2023 ACS release.

^/4The Census Bureau is planning on publishing the updated boundaries for this geographic summary level with the 2022 ACS release.