Fort Hill State Memorial is a Native American earthwork located in Highland County, Ohio, United States. Built by the Hopewell culture, it is maintained by the Arc of Appalachia Preserve System and the Ohio History Connection. 
The earthwork, built about 2,000 years ago, is a walled enclosure made of soil on top of a flat summit. It is 500 feet (150 m) higher than nearby portions of Ohio Brush Creek and 800 higher than the Ohio River.  It was made by the Hopewell people. It is over 1½ miles in circumference, enclosing 35.3 acres (14.3 ha). Thirty-nine "man-made openings" occur throughout the enclosure: thirty-six that are verified as being made by Indians and three others still unknown as to how they were made. The wall is 6–15 feet high and its total length is 8,619 feet (2,627 m). It is 30 feet wide at its base in most areas. Archaeologists believe it was not used as a fort, but instead as a religious site. 
Fort Hill State Memorial contains excellent outcrops of Silurian, Devonian, and Mississippian sedimentary bedrock and a natural bridge. The site is also an example of glacial stream reversal. It was named a National Natural Landmark in 1974. 
- "Fort Hill Earthwork - Highland County". Places to Visit. Ohio State University. Retrieved 29 July 2013.
- Ephraim George Squier; Edwin Hamilton Davis (1848). Ancient Monuments of the Mississippi Valley. Smithsonian Institution. pp. 71–75.
- National Registry of Natural Landmarks (June 2009, p. 74. Retrieved 25 November 2014.
- Official website from Arc of Appalachia Preserve System
- Fort Hill Earthworks & Nature Preserve - Ohio Historical Society
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