Fortified Hill Works, near Hamilton, Ohio, is a prehistoric hilltop earthwork preserved as a historic site and recognized on the National Register of Historic Places in 1974. Surveyed in 1847 by Ephraim George Squier and Edwin Hamilton Davis and published in their 1848 Ancient Monuments of the Mississippi Valley, it became part of early American archaeology. Its wall follows the hill’s natural shape, with an unusual outer ditch and three entrances. At the summit, investigators found a small circular enclosure and mounds, two of which contained altars with ash and sherds. Squier and Davis saw the site as both defensive and ceremonial, and linked it to the Newark Group.