70 ILCS 605/4-1
Upon the organization of the district, the temporary commissioners shall continue as permanent commissioners and shall hold office until the first Tuesday in September following the organization of the district and until their successors are selected and have qualified. On the first Tuesday in September after the organization of any district, or as soon thereafter as may be feasible, and in the manner provided in Section 3-9 of this Act, the appropriate appointing authority shall appoint 3 commissioners for such district, one of whom shall hold office for a term expiring on the first Tuesday of September next, one of whom shall hold office for a term expiring on the first Tuesday of the second succeeding September, and the other of whom shall hold office for a term expiring on the first Tuesday of the third succeeding September, and until their respective successors are selected and have qualified. On the first Tuesday of September of each succeeding year, or as soon thereafter as may be feasible, the appointing authority shall appoint one commissioner, who shall hold his office for a term expiring on the first Tuesday of the third succeeding September and until his successor is selected and has qualified.
70 ILCS 605/4-1