The Portsmouth Earthworks were constructed by the Hopewell culture (100 B.C to 500 A.D.) of prehistoric Native American people. It is a large ceremonial center located at the confluence of the Scioto and Ohio rivers. Much of the site is now encompassed by the city of Portsmouth in Scioto County, Ohio. Part of this earthwork complex extends across the Ohio River into Kentucky. Originally, the Portsmouth Earthworks included a northern section consisting of a number of circular enclosures, two large horseshoe-shaped enclosures, and three sets of parallel-walled roads leading away from this location. One set of walls went to the southwest and may have linked to a large square enclosure located on the Kentucky side of the Ohio River. Another set went to the southeast where it led to the Ohio River. The walls continued on the opposite side of the river and led to a complicated circular enclosure. The third set of walls went to the northwest for an undetermined distance.
There are few surviving remnants of the Portsmouth Earthworks. Of these, only Mound Park in Portsmouth is open to the general public. The City of Portsmouth park includes one of the large horseshoe-shaped enclosures. It is called Horseshoe Mound and it is listed on the National Register of Historic Places.
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