Cahokia Mounds State Historic Site

This is the largest prehistoric earthen construction in the Americas north of Mexico

Cahokia Mounds State

Located in Collinsville, Illinois near the city of St. Louis, this largest pre-Columbian settlement north of Mexico is the pre-eminent example of a cultural, religious, and economic centre of the Mississippian culture (800–1350), which extended throughout the Mississippi Valley and the south-eastern United States. This agricultural society may have had a population of 10,000–20,000 at its peak between 1050 and 1150, which was equivalent to the population of many European cities at that time. It once covered more than 1,600 hectares and included some 120 mounds. - in: http://whc.unesco.org/en/list/198

Monks Mound

Monks Mound is the largest Pre-Columbian earthwork in the Americas and the largest pyramid north of Mesoamerica. The beginning of its construction dates from 900-955 CE. Located at the Cahokia Mounds UNESCO World Heritage Site near Collinsville, Illinois, the mound size was calculated in 1988 as about 100 feet (30 m) high, 955 feet (291 m) long including the access ramp at the southern end, and 775 feet (236 m) wide. This makes Monks Mound roughly the same size at its base as the Great Pyramid of Giza (13.1 acres / 5.3 hectares). Its base circumference is larger than the Pyramid of the Sun at Teotihuacan. As a platform mound, the earthwork supported a wooden structure on the summit. - in: wikipedia