The OES visited Mound City on July 10, 2006. Also known as the Hopewell Culture National Historical Park, the twenty-four mounds in the park were constructed sometime between 100 BC to 500 AD over the remains of charnel houses. The Hopewell cremated their dead, burned the charnel houses and built earthen mounds over the remains. Effigy pipes, arrowheads, mica, copper figures, pottery, and other artifacts were placed within the mound. One of the more interesting items discovered was a headpiece made of human bones. Mound City is one of the largest concentrations of burial mounds to ever be discovered.
The earthworks were mapped in the early 1800s but weren't fully surveyed until 1846, at which time they were partially excavated. Many of the artifacts uncovered then were shipped to private collectors and museums overseas. Ten years after the site was surveyed, the woodland was cleared from the area and the farmer who owned the land began cultivation, causing damage to some of the mounds and embankments. In 1917, the US Army established Camp Sherman on the site as a training facility for World War I, leveling all but the large central mound. The Ohio Historical Society excavated the central mound in 1920, and by 1923, Camp Sherman had been dismantled and all of the mounds were restored according to the 1846 survey. Today the park's museum features artifacts found during excavations, a film about the Hopewell Culture, a bookstore and tours.