group of 24 cone-shaped ceremonial burial mounds (burial mound) of the Hopewell (Hopewell culture) Indians, dating from between 200 BC and AD 500, in south-central Ohio, U.S. The mounds lie along the Scioto River, just northwest of Chillicothe. Numerous pottery utensils, copper ornaments, and other artifacts have been recovered from the site, which was first explored in 1846. The park also includes the large geometric Hopeton Earthworks, which are located about 2 miles (3 km) east of the Mound City Group. The park, established as a national monument in 1923, occupies an area of 270 acres (109 hectares).