The Cahokia were an Algonquian-speaking tribe of the Illinois confederacy who were usually noted as associated with the Tamaroa tribe. At the time of European contact with the Illinois Indians, they were located in Illinois, Iowa, Missouri, and Arkansas.
Like all the confederate Illinois tribes, they were a roving people until they and the Tamaroa were gathered together into a mission settlement in about 1698 by Jesuit Priests. This mission, first known as Tamaroa, but later as Cahokia, was near the present-day site of Cahokia, Illinois, on the east bank of the Mississippi River, nearly opposite the present-day St. Louis, Missouri.
In 1721, the settlement was the second town among the Illinois in importance. On the withdrawal of the Jesuits, the tribe declined rapidly, chiefly from the demoralizing influence of a neighboring French garrison, and was nearly extinct by 1800. Five Cahokia chiefs and headmen joined those of other Illinois tribes at the 1818 Treaty of Edwardsville, Illinois, ceding to the United States half of the present state of Illinois. With the other remnant tribes of the confederacy, they moved westward in about 1820, first to Kansas and then finally to present-day Oklahoma. The Cahokia, along with the Michigamea, were eventually absorbed by the Kaskaskia and finally the Peoria. The Cahokia tribe is now considered extinct.
Another earlier tribe, also referred to as Cahokians, built one of the largest man-made earthen structures in America and a large city. Referred to today, as the Cahokia Mounds State Historic Site, it was inhabited from about A.D. 700 to 1400. Built by ancient peoples known as the Mound Builders, the city’s original population was thought to have been only about 1,000 until about the 11th century, when it dramatically expanded. At its peak, from 1,100 to 1,200 A.D., the city covered nearly six square miles and boasted a population of as many as 100,000.