Statistics for occurrence #1 of “Illinois” in chapter 5 of George Bancroft, History of the United States from the Discovery of the American Continent, Vol. 3, 15th edition.:

...askia, none existed. The English traders from Carolina were; moreover, welcomed to their villages. Nay, more: resolute in their hatred, they had even endeavored to debauch the affections of the Illinois , and to extirpate French dominion from the west. But the tawny envoys from the north descended to New Orleans, and presented the pipe of friendship. This, said Chicago to Perrier, as he concluded...
Max. Freq. Min. Freq.
Entity Corpus Doc Corpus Doc  
Illinois (Illinois, United States) 6,200 72 0 0 0 user votes
Illinois (New Mexico, United States) 4 0 0 0 0 user votes
Illinois (Oregon, United States) 2 0 0 0 0 user votes
Illinois (Colorado, United States) 0 0 0 0 0 user votes
Illinois (Illinois, United States) 0 0 0 0 0 user votes
Illinois (New Mexico, United States) 0 0 0 0 0 user votes

† This entity has been selected by the automated classifier as the most likely match in this context. It may or may not be the correct match.