Sanbornton is a town in Belknap County, New Hampshire, United States. The population was 2,966 at the 2010 census. It includes the villages of North Sanbornton and Gaza.
According to the United States Census Bureau, the town has a total area of 49.8 square miles (128.9 km), of which 47.6 sq mi (123.3 km) is land and 2.2 sq mi (5.6 km) is water, comprising 4.32% of the town. Bounded on the west by the Pemigewasset River and on the east by Winnisquam Lake, Sanbornton is largely drained by Salmon Brook, a tributary of the Pemigewasset. The highest point in town is the summit of Hersey Mountain, elevation 2,001 feet (610 m) above sea level, along the town’s northwestern border.
The town is served by Interstate 93, New Hampshire Route 132, and New Hampshire Route 127. I-93 accesses the town via Exit 22 (NH 127) and leads north to Plymouth and south to Concord. NH 132 parallels I-93 as a local road, connecting Tilton to the south with New Hampton and Ashland to the north. NH 127 intersects NH 132 in the village of Gaza within Sanbornton and leads southwest to Franklin. U.S. Route 3 crosses a very small southeastern corner of Sanbornton at the village of Winnisquam, where the road crosses Winnisquam Lake.
As of the census of 2000, there were 2,581 people, 969 households, and 749 families residing in the town. The population density was 54.3 people per square mile (21.0/km²). There were 1,359 housing units at an average density of 28.6 per square mile (11.0/km²). The racial makeup of the town was 98.14% White, 0.15% African American, 0.15% Native American, 0.50% Asian, 0.12% from other races, and 0.93% from two or more races. Hispanic or Latino of any race were 0.43% of the population.
There were 969 households out of which 33.0% had children under the age of 18 living with them, 64.7% were married couples living together, 8.9% had a female householder with no husband present, and 22.7% were non-families. 16.8% of all households were made up of individuals and 6.5% had someone living alone who was 65 years of age or older. The average household size was 2.66 and the average family size was 2.97.
In the town, the population was spread out with 25.3% under the age of 18, 6.4% from 18 to 24, 28.9% from 25 to 44, 28.4% from 45 to 64, and 10.9% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 98.4 males. For every 100 females age 18 and over, there were 97.5 males.
The median income for a household in the town was $48,458, and the median income for a family was $52,179. Males had a median income of $35,472 versus $26,117 for females. The per capita income for the town was $22,879. About 2.2% of families and 5.1% of the population were below the poverty line, including 8.4% of those under age 18 and 4.3% of those age 65 or over.