Illinois Statutes Chapter 70. Special Districts § 10/1. Definitions

(1) The term “party states” means the State of Illinois and any adjoining state; and

(2) The term “governmental unit” means any city or county located within the confines of any party state or any airport authority organized under “An Act in relation to airport authorities” approved April 4, 1945, as heretofore or hereafter amended,  1 or any comparable authority organized under the laws of another party state and authorized by the laws of such state to combine with governmental units of other party states for the purposes set forth herein: Provided, That the county, if the combining unit is a county, or if the combining unit is a city or airport authority, the county in which such city or airport authority, or the greater part thereof, is located, has a common boundary of an adjoining party state.