Summit Township was organized in 1858, and named for a relatively high point of elevation atop a drainage divide.

As of the census[1] of 2000, there were 515 people, 175 households, and 145 families residing in the township.

The racial makeup of the township was 99.61% White, 0.19% Asian, and 0.19% from two or more races.

There were 175 households, out of which 40.0% had children under the age of 18 living with them, 74.3% were married couples living together, 6.3% had a female householder with no husband present, and 16.6% were non-families.

14.3% of all households were made up of individuals, and 5.7% had someone living alone who was 65 years of age or older.