Plymouth County, Massachusetts

Plymouth County, Massachusetts
Location within the U.S. state of Massachusetts
Coordinates: 41°58′44″N 70°49′08″W / 41.978878°N 70.818954°W / 41.978878; -70.818954
Country United States
State Massachusetts
FoundedJune 2, 1685
SeatPlymouth and Brockton
Largest cityBrockton
Area
 • Total
1,093 sq mi (2,830 km2)
 • Land659 sq mi (1,710 km2)
 • Water434 sq mi (1,120 km2)  40%
Population
 (2020)
 • Total
530,819
 • Estimate 
(2024)
542,090
 • Density806.1/sq mi (311.2/km2)
Time zoneUTC−5 (Eastern)
 • Summer (DST)UTC−4 (EDT)
Congressional districts4th, 8th, 9th
Websitewww.plymouthcountyma.gov

Plymouth County is a county in the U.S. state of Massachusetts, south of Boston. As of the 2020 census, the population was 530,819. Its county seats are Plymouth and Brockton. In 1685, the county was created by the Plymouth General Court, the legislature of Plymouth Colony, predating its annexation by the Massachusetts Bay Colony.

Plymouth County is part of the Boston–Cambridge–Newton, MA–NH Metropolitan Statistical Area.