Northwood is a town in Rockingham County, New Hampshire, United States. The population was 4,241 at the 2010 census.
According to the United States Census Bureau, the town has a total area of 30.0 square miles (78 km), of which 28.0 sq mi (73 km) is land and 2.1 sq mi (5.4 km) is water, comprising 6.89% of the town. Northwood is well known for its lakes, with both seasonal and year-round residences. The larger lakes and ponds include Bow Lake, which is part of the Piscataqua River drainage basin, and Northwood Lake, Pleasant Lake, Jenness Pond, Harvey Lake, and Long Pond, all of which drain to the Suncook River, a tributary of the Merrimack River. The highest point in Northwood is Saddleback Mountain, at 1,150 feet (350 m) above sea level.
As of the census of 2000, there were 3,640 people, 1,347 households, and 1,000 families residing in the town. The population density was 130.1 people per square mile (50.2/km²). There were 1,905 housing units at an average density of 68.1 per square mile (26.3/km²). The racial makeup of the town was 97.53% White, 0.30% African American, 0.30% Native American, 0.66% Asian, 0.14% Pacific Islander, 0.19% from other races, and 0.88% from two or more races. Hispanic or Latino of any race were 0.55% of the population.
There were 1,347 households out of which 36.7% had children under the age of 18 living with them, 62.0% were married couples living together, 7.7% had a female householder with no husband present, and 25.7% were non-families. 18.0% of all households were made up of individuals and 5.1% had someone living alone who was 65 years of age or older. The average household size was 2.70 and the average family size was 3.07.
In the town, the population was spread out with 27.1% under the age of 18, 6.6% from 18 to 24, 32.1% from 25 to 44, 25.2% from 45 to 64, and 9.0% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 100.3 males. For every 100 females age 18 and over, there were 99.3 males.
The median income for a household in the town was $50,675, and the median income for a family was $53,953. Males had a median income of $36,161 versus $27,721 for females. The per capita income for the town was $21,491. About 1.5% of families and 4.2% of the population were below the poverty line, including 3.0% of those under age 18 and 3.0% of those age 65 or over.