A confederation of Native North Americans, comprising the Cahokia, the Kaskaskia, the Michigamea, the Moingwena, the Peoria, and the Tamaroa tribes.
They belong to the Algonquian branch of the Algonquian-Wakashan linguistic stock .
In the mid-17th cent. they lived in S. Wisconsin, N. Illinois, and sections of Iowa and Missouri.
They then numbered some 6,500.
Jacques Marquette and Louis Jolliet are believed to have been the first Europeans to travel (1673) through Illinois territory.
Father Claude Jean Allouez, a Jesuit missionary, visited them in 1676 and stayed with them for years.
By 1750 wars with the Sioux, the Fox, and the Iroquois had reduced the population to some 2,000.
In 1769 the assassination of the celebrated Ottawa chief Pontiac by a Kaskaskia provoked the Lake tribes (the Ojibwa, the Ottawa, the Potawatami, the Kickapoo, and the Sac and Fox) to vengeance.
They began a war of extermination, which in a few years diminished the Illinois to a small number, who sought asylum at the French settlement at Kaskaskia.
By 1800 there remained some 150 Illinois.
In 1833 the survivors, represented by the Kaskaskia and the Peoria, sold their lands in Illinois and moved W. of the Mississippi.
Their descendants now occupy a reservation in N.E. Oklahoma, which they share with the Wea and Piankashaw.