The people who built Cahokia are known to archaeologists as the Mississippians — a label that refers not to a single ethnic group or political community but to a broad cultural tradition that spread across much of what is now the eastern and central United States between approximately 800 CE and the period of European contact.

The Mississippian tradition was characterized by specific patterns of mound building, by the cultivation of corn as a staple crop, by distinctive pottery styles and artistic traditions, by extensive trade networks, and by forms of social and political organization that varied considerably from one community to another.

The people of Cahokia were one specific community within this broader cultural tradition.

They spoke languages that were ancestral to some of the languages spoken today by Native nations of the eastern and central United States — languages of the Siouan family are one possibility that archaeologists and linguists have considered, though the specific linguistic identity of the Cahokians cannot be determined with certainty from the physical evidence.