 Penn Township was named for William Penn (1644–1718), founder of Pennsylvania.According to the United States Census Bureau, the township has a total area of 36.1 square miles (93.4 km²), of which 35.2 square miles (91.1 km²) of it is land and 0.9 square miles (2.4 km²) of it (2.55%) is water.As of the census of 2000, there were 309 people, 119 households, and 87 families residing in the township.