CITY · MA

What county is Boston, MA in?

Boston, MA is mostly in Suffolk County. County FIPS code 25025, population 768,425 (2023 estimate).

County details

City: Boston, Massachusetts
Primary county: Suffolk County
FIPS code: 25025
County population: 768,425

Some cities extend into more than one county. Boston is placed in the county that contains its center. For a specific address, use the address lookup.

Questions

What county is Boston in?

Boston, MA is mostly in Suffolk County.

What is the county seat of Suffolk County?

County seats are not part of the data on this site. Check the county’s official website.

Can a city be in two counties?

Yes. Large cities such as Houston and Atlanta cross county lines. The address lookup shows the exact county for any street address.

Sources: U.S. Census Bureau geographic reference files; FCC Area API; Census Bureau Population Estimates, Vintage 2023. Last reviewed 2026-10-27.