The exceptional environmental setting of the North Plaza, Cahokia Mounds, Illinois, USA

Plazas are ubiquitous elements of community layout, defined as open space surrounded by or adjacent to structures. Functionally, plazas serve as public space for gatherings and ceremonial activities. At Cahokia Mounds, the largest pre-contact site in North America, the North Plaza puzzled archaeologists because of its unique location in a wetland. The construction of a mound and plaza group in an area inundated with water is unprecedented in the Eastern-Woodlands archaeological record and contradicts traditional conceptions of plaza space. Previous scholars dealt with this conundrum by hypothesizing that the North Plaza was drier during its construction and occupation than in modern times. However, evidence from sedimentological analysis and stable carbon isotopes of buried soils suggests the North Plaza was an inundated feature on the landscape throughout Cahokia’s occupation. The North Plaza is an anomaly in the Eastern-Woodlands that now requires archaeologists to re-envision what plazas are and how they are used.