New Castle is a town in Westchester County, New York, United States. The population was 17,569 at the 2010 census. It includes the hamlets of Chappaqua and Millwood.
According to the United States Census Bureau, the town has a total area of 23.5 square miles (61 km), of which 23.2 square miles (60 km) is land and 0.3 square miles (0.78 km), or 1.15%, is water. New Castle is bordered by the towns of Mount Pleasant and Ossining to the southwest and North Castle to the southeast. It is bordered by the towns of Bedford, Mount Kisco, and Somers to the northeast and Yorktown and Cortlandt to the northwest.
As of the census of 2000, there were 17,491 people, 5,732 households, and 4,929 families residing in the town. The population density was 754.8 people per square mile (291.5/km²). There were 5,843 housing units at an average density of 252.2 per square mile (97.4/km²). The racial makeup of the town was 91.50% White, 1.37% African American, 0.05% Native American, 5.55% Asian, 0.02% Pacific Islander, 0.51% from other races, and 1.00% from two or more races. Hispanic or Latino of any race were 2.78% of the population.
There were 5,732 households out of which 49.6% had children under the age of 18 living with them, 79.0% were married couples living together, 5.3% had a female householder with no husband present, and 14.0% were non-families. 11.4% of all households were made up of individuals and 4.6% had someone living alone who was 65 years of age or older. The average household size was 3.04 and the average family size was 3.28.
In the town, the population was spread out with 31.9% under the age of 18, 3.6% from 18 to 24, 25.4% from 25 to 44, 29.9% from 45 to 64, and 9.2% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 97.8 males. For every 100 females age 18 and over, there were 92.2 males.
The median income for a household in the town was $159,691, and the median income for a family was $174,579. Males had a median income of $100,000 versus $67,275 for females. The per capita income for the town was $73,888. About 2.0% of families and 3.5% of the population were below the poverty line, including 4.6% of those under age 18 and 3.6% of those age 65 or over.