55 ILCS 5/1-3011
For the purpose of fixing the permanent location of the county seat of such new county, the voters of said county shall, at said election for county officers, vote for some place, to be designated upon their ballots, for a county seat; upon which ballot shall be written or printed, or partly written and partly printed, "For County Seat," after which words shall be written or printed the name of the place intended for the county seat. The place receiving a majority of all the legal votes cast upon the question shall be the county seat of said county. But if no place shall receive a majority of all the votes cast upon the question, then it shall be the duty of the county board of said county to choose from the two places having the greatest number of legal voters at the former election; and the place so chosen shall be the permanent county seat of said county.
55 ILCS 5/1-3011