The population count of Plymouth County, MA was 506,657 in 2016. The population count of Worcester County, MA was 813,589 in 2016. The population count of Hillsborough County, NH was 404,948 in 2016. The population count of Rockingham County, NH was 300,365 in 2016.
Population
Population Change
Above charts are based on data from the U.S. Census American Community Survey | ODN Dataset | API -