Fort Thompson Mounds

The Fort Thompson Mounds are a complex of ancient archaeological sites in Buffalo County, South Dakota, near Fort Thompson and within the Crow Creek Reservation. Declared a National Historic Landmark in 1964 by the US Department of Interior, the mound complex extends for a distance of about 6 miles (9.7 km) along the east bank of the Missouri River. It is one of the largest known complex of burial mounds in the Plains region north of Kansas. One of the sites excavated in the 1950s was radiocarbon dated to c. 2450 BCE, showing nearly 5,000 years of indigenous human settlement. The mounds are believed to have been constructed in the Plains-Woodland period, beginning c. 800 CE.