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 to 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). The perimeter of its base is larger than the Pyramid of the Sun at Teotihuacan. As a platform mound, the earthwork supported a wooden structure on the summit.
Monks Mound in summer. The concrete staircase follows the approximate course of the ancient wooden stairs | |
Location within Illinois today | |
| Location | Collinsville, Illinois, Madison County, Illinois, United States |
|---|---|
| Region | Madison County, Illinois |
| Coordinates | 38°39′38.4″N 90°3′43.36″W |
| History | |
| Founded | 900–950 CE |
| Cultures | Mississippian culture |
| Site notes | |
| Archaeologists | Thomas I. Ramey |
| Architecture | |
| Architectural styles | Platform mound |
| Responsible body: Illinois Historic Preservation Agency | |
Unlike Egyptian pyramids which were built of stone, the platform mound was constructed almost entirely of layers of basket-transported soil and clay. Because of this construction and its flattened top, over the years, it has retained rainwater within the structure. This has caused slumping, the avalanche-like sliding of large sections of the sides at the highest part of the mound. Its designed dimensions would have been significantly smaller than its present extent, but recent excavations have revealed that slumping was a problem even while the mound was being made.