The park contains a winding prehistoric Indian hilltop fortification named after the nearby town of Carlisle. Carlisle Fort features remnants of earthen walls built around 2,000 years ago by the Hopewell Indians. The first published descriptions of Carlisle Fort come from a letter written in 1835 by historian S. H. Binkley. Early historians, like Binkley, believed that these enclosure sites were made to defend the hilltop, and so the term “fort” was commonly used in the name. Later archaeological work shows that hilltop enclosures were used for ceremonial purposes.

On February 26, 1974, the National Park Service listed the Carlisle Fort site in the National Register of Historic Places. Today the site is preserved as part of Twin Creek MetroPark. When visiting the site, you can clearly see the low, earthen embankments that follow the edge of the ravine. This ridge is about two feet high and is missing some sections due to erosion. Following Twin Creek MetroPark’s green hiking trail to the left will take you through a gateway in the mounds after trail marker #6. From there, the green trail proceeds down to Twin Creek.