There are 14 counties in Massachusetts. In 2019, Middlesex County is the most populous county in Massachusetts with a population of 1,614,614. This represents an increase in the population of 7.1% since the 2010 census. Following Middlesex County, which is home to the city of Lowell and part of the Boston-Cambridge metro area, are Worcester County (830,839) with the city of Worcester, Suffolk County (807,252) with the city of Boston, Essex County (790,638) with the cities of Salem and Lynn, and Norfolk County (705,388). Massachusetts is also home to two other counties with more than 500,000 residents and four other counties with 100,000 to 499,999 residents. Of the five largest counties, Suffolk County experienced the greatest population growth of 11.22% since 2010.
The county that has the fewest residents in Massachusetts is Nantucket County. Since 2010’s census, Nantucket County has experienced a growth rate of 11.41%, making it the fastest-growing county in the state. Nantucket County's population in 2019 is 11,327. Following Nantucket County as the county with the fewest residents in Massachusetts are Dukes County (17,352), Franklin County (70,963), and Berkshire County (126,348). Of these counties, Berkshire County had the most significant population loss of -3.79%.
Nantucket County has seen the most rapid rate of growth in Massachusetts, having grown by 11.41% since the 2010 United States census, with the population standing at 11,327 in 2019. Suffolk County (11.22%), Middlesex County (7.10%), and Essex County (6.06%) all follow. Berkshire County has seen the lowest rate of growth with a population growth rate of -3.79% since 2010.