Thornton is a town in Grafton County, New Hampshire, United States. The population was 2,490 at the 2010 census.
According to the United States Census Bureau, the town has a total area of 50.8 square miles (131.6 km), of which 50.2 square miles (130.0 km) is land and 0.6 square miles (1.6 km) is water, comprising 1.19% of the town. The highest point in Thornton is 2,580 feet (790 m) above sea level on the western ridge of Dickey Mountain, whose 2,734-foot (833 m) summit lies in the neighboring town of Waterville Valley.
As of the census of 2000, there were 1,843 people, 759 households, and 507 families residing in the town. The population density was 36.6 people per square mile (14.1/km²). There were 1,487 housing units at an average density of 29.5 per square mile (11.4/km²). The racial makeup of the town was 97.61% White, 0.27% African American, 0.11% Native American, 0.27% Asian, 0.05% Pacific Islander, 0.33% from other races, and 1.36% from two or more races. Hispanic or Latino of any race were 0.71% of the population.
There were 759 households out of which 29.6% had children under the age of 18 living with them, 56.5% were married couples living together, 6.6% had a female householder with no husband present, and 33.2% were non-families. 21.1% of all households were made up of individuals and 6.6% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 2.86.
In the town, the population was spread out with 22.4% under the age of 18, 7.5% from 18 to 24, 33.1% from 25 to 44, 24.6% from 45 to 64, and 12.4% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 99.2 males. For every 100 females age 18 and over, there were 102.5 males.
The median income for a household in the town was $38,380, and the median income for a family was $45,172. Males had a median income of $27,750 versus $22,938 for females. The per capita income for the town was $18,478. About 6.9% of families and 9.5% of the population were below the poverty line, including 13.5% of those under age 18 and 3.0% of those age 65 or over.