It was originally named Ottawa or Ottaway in the 1840 census and was organized as Otto Township in 1860.

As of the census[1] of 2000, there were 662 people, 247 households, and 183 families residing in the township.

There were 302 housing units at an average density of 8.4 per square mile (3.3/km2).

There were 247 households, out of which 36.0% had children under the age of 18 living with them, 62.3% were married couples living together, 6.5% had a female householder with no husband present, and 25.9% were non-families.

21.5% of all households were made up of individuals, and 6.5% had someone living alone who was 65 years of age or older.