Merrimack is a town in Hillsborough County, New Hampshire, United States. The population was 25,494 at the 2010 census, making it the eighth-largest municipality in New Hampshire. In 2013, Merrimack was named the twenty-third best place to live in the United States by CNN Money Magazine.
There are four villages in the town: Merrimack Village (formerly known as Souhegan Village), Thornton's Ferry, Reed's Ferry, and South Merrimack.
As of the census of 2000, there were 25,119 people, 8,832 households, and 6,986 families residing in the town. The population density was 770.6 people per square mile (297.5/km²). There were 8,959 housing units at an average density of 274.8 per square mile (106.1/km²). The racial makeup of the town was 96.58% White, 0.73% African American, 0.19% Native American, 1.50% Asian, 0.04% Pacific Islander, 0.21% from other races, and 0.74% from two or more races. Hispanic or Latino of any race were 1.08% of the population.
There were 8,832 households out of which 41.9% had children under the age of 18 living with them, 68.1% were married couples living together, 7.8% had a female householder with no husband present, and 20.9% were non-families. 15.8% of all households were made up of individuals and 3.8% had someone living alone who was 65 years of age or older. The average household size was 2.84 and the average family size was 3.19.
In the town the population was spread out with 29.0% under the age of 18, 5.8% from 18 to 24, 34.2% from 25 to 44, 24.7% from 45 to 64, and 6.4% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 99.3 males. For every 100 females age 18 and over, there were 96.7 males.
The median income for a household in the town was $68,817, and the median income for a family was $72,011. Males had a median income of $51,725 versus $31,528 for females. The per capita income for the town was $27,748. About 1.2% of families and 1.9% of the population were below the poverty line, including 2.9% of those under age 18 and 3.1% of those age 65 or over.