Cahokia Mounds, approximately 85 Native American earthworks in Cahokia Mounds State Historic Site, SW Ill., near East St. Louis; largest group of mounds N of Mexico. Monks' Mound, a rectangular, flat-topped earthwork, 100 ft (30.5 m) high with a 17-acre (6.9-hectare) base, is named for Trappist monks who settled there in the early 19th cent. The people who constructed the mounds were village dwellers who lived in a fertile river-bottom area; their culture flourished from c.1300 to c.1700. The mounds constitute a national historic landmark.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.