Cahokia, a native American city of around 20,000 residents, may have been the first center of multiculturalism in North America. Almost a thousand years ago, the city was larger than any enclave in America would be until just before the American Revolution. 

The site was populated well before the arrival of Christopher Columbus, reaching its heyday around the year 1050. The city was located near modern-day St. Louis.

Monk's Mound was the ceremonial center of Cahokia. Residents spent three hundred years constructing the monument, featuring terraces and plazas. Monk's Mound consisted of at least 120 structures, stretched over five square miles. One mound at the center climbs ten stories into the air. The structure is located just seven miles from St. Louis' famous Gateway Arch. Two other, smaller facilities are located within just a few miles. These make up three of the four largest native American mound centers known to archeologists. 

"Many of these mounds were topped by temples or the houses of the elites and were arranged around large ceremonial plazas where great community political, social and religious events were held," Thomas Emerson, director of the Illinois State Archaeological Survey, wrote to Live Science. 

Nestled among the ceremonial buildings were thatch-covered houses, homes for both commoners and elites. Other finds include beakers of a caffeinated drink brewed to induce ritual vomiting. Feasting pits show evidence that up to 100 deer were cooked at a single time to feed the masses. 

One of the great mysteries is what drove all these people to gather in the bottom lands of the lower Mississippi. There are no written records from the civilization, and investigation of artifacts has not yet yielded a definitive answer. 

Trade may have played a role in attracting people to the area. Goods from Cahokia have been found in modern-day Oklahoma, Wisconsin and Iowa. Artifacts from those regions have also been discovered in the lower Mississippi structure. 

Thomas Emerson, an archaeologist from Illinois State, led a study of Cahokia. His team looked at strontium levels in dozens of teeth recovered from human remains. As people and animals eat, they consume two different isotopes of the element, strontium-86 and strontium-87. Different locations have varying ratios of these two forms of the metal. By measuring the relative levels of the two isotopes, it is possible to determine where an individual spent most of their lives. 

Results indicate that for three centuries, Cahokia was regularly visited by immigrants, many of whom chose to stay in the area. New residents may have arrived in the complex from around the midwest. Some may have come from as far west as the Gulf Coast, and as far north as the Great Lakes. Over the course of three hundred years, as many as one-third of all the people living in Cahokia were from somewhere else, according to the study.