Cahokia reached its greatest size and density sometime between 1050 and 1200 CE — the period that archaeologists refer to as the Lohmann and Stirling phases.

The population estimates for this period vary significantly depending on the methodology used and the assumptions made, but the most commonly cited range for the city center is between 10,000 and 20,000 people, with the broader settlement zone in the American Bottom — encompassing the satellite communities and agricultural villages that surrounded and supplied the urban core — holding perhaps 50,000 to 100,000 people in total.

These numbers require some context to appreciate.

In 1100 CE, the city of London had an estimated population of perhaps 15,000 to 18,000 people.