[4] Overisel is the birthplace of mathematician George David Birkhoff, best known for what is now called the ergodic theorem.

[3] As of the census[1] of 2000, there were 2,594 people, 869 households, and 730 families residing in the township.

There were 897 housing units at an average density of 25.0 per square mile (9.7/km2).

There were 869 households, out of which 42.7% had children under the age of 18 living with them, 77.7% were married couples living together, 3.5% had a female householder with no husband present, and 15.9% were non-families.

13.8% of all households were made up of individuals, and 6.3% had someone living alone who was 65 years of age or older.