50 ILCS 10/2
Membership of the council shall consist of one representative from each governmental unit or private regional organization entering into the agreement. Private regional organizations shall be selected by the elected public official members and shall not exceed 33% of the total membership. The representative from each governmental unit shall be the elected chief executive of the member governmental unit.
Each member governmental unit annually may designate one of its elected officials, for a term ending on the last day of the council's fiscal year, as an alternate representative to act at any council meeting in the absence therefrom of the elected chief executive.
If such governmental unit does not have an elected chief executive, a member of its governing body shall be chosen by such body to be its representative. Any governmental unit which has become a member of the council may withdraw upon 60 days notice after formal action by its governing body. Representatives from local, state, and federal agencies, commissions, and boards are eligible to serve as ex officio members.
50 ILCS 10/2