Theresa is a town in Jefferson County, New York, United States. The population was 2,905 at the 2010 census, up from 2,414 at the 2000 census. The town is named after Theresa La Ray, the daughter of an original landowner.
According to the United States Census Bureau, the town has a total area of 69.7 square miles (180.6 km), of which 64.9 square miles (168.2 km) are land and 4.8 square miles (12.4 km), or 6.87%, are water.
The northeast town line is the border of St. Lawrence County.
The Indian River flows northeasterly through the town. Most of the northeast part of the town is covered by lakes or swampland.
New York State Route 26 and New York State Route 37, partially combined, are north-south highways in Theresa. New York State Route 411 is an east-west highway that ends at NY-37, west of Theresa village. NY-411 intersects Interstate 81 at the west town line.
As of the census of 2000, there were 2,414 people, 869 households, and 641 families residing in the town. The population density was 36.9 people per square mile (14.2/km²). There were 1,646 housing units at an average density of 25.2 per square mile (9.7/km²). The racial makeup of the town was 97.14% White, 1.70% Black or African American, 0.25% Native American, 0.25% Asian, 0.12% from other races, and 0.54% from two or more races. Hispanic or Latino of any race were 0.58% of the population.
There were 869 households out of which 38.1% had children under the age of 18 living with them, 57.8% were married couples living together, 9.0% had a female householder with no husband present, and 26.2% were non-families. 18.9% of all households were made up of individuals and 6.0% had someone living alone who was 65 years of age or older. The average household size was 2.78 and the average family size was 3.13.
In the town, the population was spread out with 30.2% under the age of 18, 7.1% from 18 to 24, 32.1% from 25 to 44, 22.9% from 45 to 64, and 7.6% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 108.5 males. For every 100 females age 18 and over, there were 105.2 males.
The median income for a household in the town was $36,953, and the median income for a family was $39,519. Males had a median income of $29,698 versus $22,841 for females. The per capita income for the town was $17,027. About 14.1% of families and 15.3% of the population were below the poverty line, including 16.9% of those under age 18 and 1.6% of those age 65 or over.