From Ohio History Central
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| image = [[File:Fort Ancient Walls.jpg]]
| caption = Postcard showing the great east walls of Fort Ancient,
ca. 1920-1950. Fort Ancient, built 2,000 years ago by prehistoric Native Americans, is an earthworks with 18,000 feet of earthen walls enclosing 100 acres. It is located in Warren County, Ohio and maintained as a state memorial by the Ohio Historical Society.