Seaford is a census-designated place (CDP) within both in the Oyster Bay and Hempstead Nassau County, New York, United States. The population was 15,294 at the 2010 census. It is serviced by the Seaford Station on the Long Island Rail Road.
Seaford is located at 40°40′7″N 73°29′33″W / 40.66861°N 73.49250°W / 40.66861; -73.49250 (40.668702, -73.492459).
According to the United States Census Bureau, the CDP has a total area of 2.6 square miles (6.7 km), of which 2.6 square miles (6.7 km) is land and 0.38% is water.
As of the census of 2000, there were 15,791 people, 5,257 households, and 4,200 families residing in the CDP. The population density was 6,072.9 per square mile (2,345.0/km²). There were 5,358 housing units at an average density of 2,060.6/sq mi (795.7/km²). The racial makeup of the CDP was 99.80% White, 0.15% African American, 0.06% Native American, 0.68% Asian, 0.02% Pacific Islander, 0.54% from other races, and 0.59% from two or more races. Hispanic or Latino people of any race were 1.71% of the population.
There were 5,257 households out of which 37.2% had children under the age of 18 living with them, 68.4% were married couples living together, 8.6% had a female householder with no husband present, and 20.1% were non-families. 16.3% of all households were made up of individuals and 8.3% had someone living alone who was 65 years of age or older. The average household size was 3.00 and the average family size was 3.38.
In the CDP, the population was spread out with 25.2% under the age of 18, 6.9% from 18 to 24, 30.2% from 25 to 44, 23.9% from 45 to 64, and 13.7% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 95.5 males. For every 100 females age 18 and older, there were 93.0 males.
The median income for a household in the CDP was $78,572, and the median income for a family was $85,751. Males had a median income of $60,092 versus $39,083 for females. The per capita income for the CDP was $29,244. About 2.8% of families and 3.6% of the population were below the poverty line, including 2.9% of those under age 18 and 3.9% of those age 65 or over.