Ill. Const. art. VI, § 7

(a) The State shall be divided into Judicial Circuits consisting of one or more counties. The First Judicial District shall constitute a Judicial Circuit. The Judicial Circuits within the other Judicial Districts shall be as provided by law. Circuits composed of more than one county shall be compact and of contiguous counties. The General Assembly by law may provide for the division of a circuit for the purpose of selection of Circuit Judges and for the selection of Circuit Judges from the circuit at large.

(b) Each Judicial Circuit shall have one Circuit Court with such number of Circuit Judges as provided by law. Unless otherwise provided by law, there shall be at least one Circuit Judge from each county. In the First Judicial District, unless otherwise provided by law, Cook County, Chicago, and the area outside Chicago shall be separate units for the selection of Circuit Judges, with at least twelve chosen at large from the area outside Chicago and at least thirty-six chosen at large from Chicago.

(c) Circuit Judges in each circuit shall select by secret ballot a Chief Judge from their number to serve at their pleasure. Subject to the authority of the Supreme Court, the Chief Judge shall have general administrative authority over his court, including authority to provide for divisions, general or specialized, and for appropriate times and places of holding court.