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There are 10 counties in New Hampshire. The most populous county in New Hampshire is Hillsborough County, which is home to 415,427 residents. This is about 30.61% of the state’s total population. Since 2010, Hillsborough County has grown 3.54%. The second-most populous county in New Hampshire is Rockingham County with a population of 309,176 people, about 22.79% of the population, followed by Merrimack County with 151,132 people, about 11.14% of the state population. Both Rockingham and Merrimack have grown since the 2010 Census by 4.70% and 3.24%, respectively.
Of New Hampshire’s 10 counties, Coos County has the fewest residents at 31,589. This is about 2.33% of the state’s total population. The population density is 17.60 persons per square mile. The second-least populated county in New Hampshire is Sullivan County, which is home to 43,144 people, about 3.18% of the state’s total population. This is followed by Carroll County with a population of 48,799 people.
Seven out of the 10 New Hampshire counties have experienced growth since the 2010 Census. Strafford County experienced the highest population growth of 5.60%, followed by Rockingham County with 4.70% and Hillsborough County with 3.54%.
The three counties that experienced a population decline since 2010 are Coos County (4.20%), Sullivan County (1.41%), and Cheshire County (0.73%)