Coordinates: 42°12′52″N 78°38′11″W / 42.21444°N 78.63639°W / 42.21444; -78.63639
According to the United States Census Bureau, the town has a total area of 49.67 square miles (128.65 km), of which 49.63 square miles (128.55 km) is land and 0.035 square miles (0.09 km), or 0.07%, is water.
The Allegheny River flows through the southeast corner of the town, and Great Valley Creek is an important stream in the town.
U.S. Route 219 is a major north-south highway in the town and intersects New York State Route 98 in Great Valley village.
As of the census of 2000, there were 2,145 people, 843 households, and 596 families residing in the town. The population density was 42.8 people per square mile (16.5/km²). There were 1,196 housing units at an average density of 23.8 per square mile (9.2/km²). The racial makeup of the town was 96.36% White, 0.79% African American, 1.17% Native American, 0.70% Asian, 0.47% from other races, and 0.51% from two or more races. Hispanic or Latino of any race were 0.93% of the population.
There were 843 households out of which 30.0% had children under the age of 18 living with them, 58.8% were married couples living together, 7.4% had a female householder with no husband present, and 29.2% were non-families. 24.0% 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 2.52 and the average family size was 2.98.
In the town, the population was spread out with 25.0% under the age of 18, 6.4% from 18 to 24, 26.9% from 25 to 44, 27.2% from 45 to 64, and 14.5% who were 65 years of age or older. The median age was 41 years. For every 100 females, there were 109.7 males. For every 100 females age 18 and over, there were 103.7 males.
The median income for a household in the town was $37,784, and the median income for a family was $42,209. Males had a median income of $31,581 versus $21,792 for females. The per capita income for the town was $17,749. About 3.1% of families and 6.7% of the population were below the poverty line, including 4.9% of those under age 18 and 6.3% of those age 65 or over.