55 ILCS 5/5-14003
If such region is situated in or embraces more than one county, the county boards of said counties are hereby empowered to cooperate in defining the boundaries of said region, and in the creation and organization of one joint regional planning commission for such region so mutually defined. The county boards of the counties which are members of the joint regional planning commission are authorized to appropriate from their funds for the use of the joint regional planning commission, in the amounts as may mutually be agreed upon by said county boards.
The joint regional planning commission is authorized to prepare zoning and building codes, ordinances or resolutions for submission to and adoption by the various member county boards. The joint regional planning commission may employ a staff to assist the member county boards in the administration and enforcement of such zoning and building codes or ordinances throughout the district, and in each member county.
55 ILCS 5/5-14003