Prairie du Sac is a town in Sauk County, Wisconsin, United States. The population was 1,138 at the 2000 census. The Village of Prairie du Sac is located within the town. The unincorporated community of Loddes Mill is also located in the town.
According to the United States Census Bureau, the town has a total area of 30.4 square miles (78.6 km²), of which, 29.5 square miles (76.4 km²) of it is land and 0.9 square miles (2.2 km²) of it (2.83%) is water.
As of the census of 2000, there were 3,231 people, 415 households, and 337 families residing in the town. The population density was 38.6 people per square mile (14.9/km²). There were 428 housing units at an average density of 14.5 per square mile (5.6/km²). The racial makeup of the town was 97.89% White, 0.09% Black or African American, 0.88% Asian, and 1.14% from two or more races. 0.18% of the population were Hispanic or Latino of any race.
There were 415 households out of which 36.1% had children under the age of 18 living with them, 73.5% were married couples living together, 4.8% had a female householder with no husband present, and 18.6% were non-families. 15.2% 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 2.74 and the average family size was 3.07.
In the town, the population was spread out with 26.4% under the age of 18, 5.0% from 18 to 24, 30.8% from 25 to 44, 27.6% from 45 to 64, and 10.2% who were 65 years of age or older. The median age was 35 years. For every 100 females, there were 106.9 males. For every 100 females age 18 and over, there were 107.4 males.