St. Mathias Township took its name from a local Roman Catholic church.

As of the census[1] of 2000, there were 490 people, 169 households, and 138 families residing in the township.

There were 169 households, out of which 41.4% had children under the age of 18 living with them, 71.6% were married couples living together, 5.3% had a female householder with no husband present, and 18.3% were non-families.

14.2% of all households were made up of individuals, and 4.7% had someone living alone who was 65 years of age or older.

Males had a median income of $35,625 versus $20,938 for females.