Penn Township is one of thirteen townships in Parke County, Indiana, USA. As of the 2000 census, its population was 868.According to the United States Census Bureau, Penn Township covers an area of 23.77 square miles (61.6 km2); of this, 23.72 square miles (61.4 km2) (99.77 percent) is land and 0.05 square miles (0.13 km2) (0.23 percent) is water. The township includes the southwest quarter of Turkey Run State Park. Parke County is a county in the western part of the U.S. state of Indiana. It was formed in 1821 out of a portion of Vigo County. The county seat is Rockville.