The township is named after war hero Stephen Decatur, Jr.

According to the United States Census Bureau, the township has a total area of 38.1 square miles (99 km2), all land.

New Castle (Clearfield County)[3] As of the census[5] of 2000, there were 2,974 people, 1,210 households, and 861 families residing in the township.

There were 1,316 housing units at an average density of 34.5 per square mile (13.3/km2).

24.4% of all households were made up of individuals, and 12.8% had someone living alone who was 65 years of age or older.