Gennessee Township was organized in 1858, and named after the Genesee River in New York, the home state of a share of the early settlers.

As of the census[2] of 2000, there were 458 people, 164 households, and 132 families residing in the township.

There were 182 housing units at an average density of 5.6 per square mile (2.2/km2).

There were 164 households, out of which 38.4% had children under the age of 18 living with them, 62.8% were married couples living together, 10.4% had a female householder with no husband present, and 19.5% were non-families.

15.9% of all households were made up of individuals, and 4.3% had someone living alone who was 65 years of age or older.