70 ILCS 2205/5
There shall be 5 trustees, elected as provided in this Section, who shall constitute a board of trustees for the sanitary district. The trustees shall hold office for 4 years, and until their successors are elected and qualified. At all regular elections held after August 20, 1965, 3 trustees shall be elected from the territory of the district in the county having the greater assessed valuation of the district and 2 trustees shall be elected from the territory of the district in the county having the lesser assessed valuation of the district. However, all trustees shall be elected from the district as a whole if the equalized assessed valuation of the district for taxation purposes is less than $100,000,000. The election of trustees to succeed the first board of trustees shall be held at the election provided by the general election law in the year their term expires, and every 4 years thereafter. The trustees shall choose one of their number as president and one as vice-president. In case of the death, resignation, absence from the state, or other disability of the president, the powers, duties and emoluments of the office of president shall devolve upon the vice-president, until such disability is removed or until a successor to the president is elected or appointed and chosen in the manner provided in this Act. All elections for trustees of such sanitary districts shall be held under the provisions of the general election laws of this State.
In the event there is to be a division of trustees between the counties having a territory within the district, only those voters residing within the limits of the territory of such sanitary district within a county shall be allowed to vote for trustees of the sanitary district, elected from such county. If all trustees are elected at large in the district, any voter residing within the limits of the district may vote for the trustees of his choice irrespective of his county of residence.
In case of a vacancy in the office of trustee of any sanitary district the county clerk of the county in which the trustee whose office is vacant resided shall notify the Governor of any such vacancy, whereupon the Governor shall issue a writ of election to the county clerk of the county in which such vacancy exists, who shall conduct an election to fill such vacancy at the next regular election provided in the general election law for the election of such trustees. If such vacancy occurs within 28 months before the expiration of the term of the office made vacant, the Governor shall fill such vacancy by appointment.
70 ILCS 2205/5