Merrimack County is a county in the U.S. state of New Hampshire which has two cities and twenty-five towns. In 2006 the population was 148,085. Its county seat is Concord. The center of population of New Hampshire is located in Merrimack County, in the town of Pembroke.
Merrimack County was organized at Concord in 1823, and is named for the Merrimack River. It was formed by removing towns from northern Hillsborough and Rockingham Counties. In 1841 its original scope was somewhat reduced by the creation of Belknap County.
The county has a total area of 956 square miles (2,476 km2), of which 934 sq mi (2,419 km2) is land and 22 sq mi (57 km2) (2.31%) is water.
As of the census of 2000, there were 136,225 people, 51,843 households, and 35,460 families residing in the county. The population density was 146 people per square mile (56/km²). There were 56,244 housing units at an average density of 60 per square mile (23/km²). The racial makeup of the county was 97.08% White, 0.54% Black or African American, 0.23% Native American, 0.86% Asian, 0.02% Pacific Islander, 0.23% from other races, and 1.04% from two or more races. 1.00% of the population were Hispanic or Latino of any race. 16.5% were of English, 13.4% Irish, 12.7% French, 11.0% French Canadian, 8.4% American, 6.4% German and 6.0% Italian ancestry according to Census 2000. 94.2% spoke English, 2.9% French and 1.1% Spanish as their first language.
There were 51,843 households out of which 33.90% had children under the age of 18 living with them, 54.90% were married couples living together, 9.80% had a female householder with no husband present, and 31.60% were non-families. 24.60% of all households were made up of individuals and 9.00% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 3.00.
In the county the population was spread out with 24.90% under the age of 18, 8.10% from 18 to 24, 30.60% from 25 to 44, 24.00% from 45 to 64, and 12.40% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 97.00 males. For every 100 females age 18 and over, there were 93.70 males.
The median income for a household in the county was $48,522, and the median income for a family was $56,842. Males had a median income of $37,722 versus $27,207 for females. The per capita income for the county was $23,208. About 4.10% of families and 5.90% of the population were below the poverty line, including 6.60% of those under age 18 and 5.70% of those age 65 or over.