Around the year 1050, Cahokia became one of the most powerful pre-European contact cities ever built in what would become the United States. Before then, it was still a sizable settlement, but with no more than one thousand residents. At its height, Cahokia may have been home to as many as 20,000 people, who are today referred to as Mississippians. Archaeologists and anthropologists think this is largely the cause of what has become known as the cultural Big Bang.
For many years, researchers have thought that it was large-scale immigration to the site which caused this growth. Evidence suggests that in the eleventh century many people left their countryside settlements in favor of settling in Cahokia and the surrounding Mississippi River neighborhoods. Bone and pottery analysis indicates that most of these people came from the surrounding Mid-West area. However, some may have come from as far away as the Gulf Coast and Great Lakes.
It is very likely that Cahokia's strength and influence came from being a growing city of immigrants. Archaeological evidence suggests that influxes of immigrants came to Cahokia as early as the eleventh century and continued right up until its collapse in the fourteenth century. Immigrants became well integrated into Cahokia's society and helped maintain a large and stable population.
As a large city, Cahokia was able to extend its influence across the region. It became a commercial center with extensive trade networks. This further helped the Mississippian culture spread throughout the region.