65 ILCS 5/11-69-1
Whenever the territories of any 2 or more municipalities in the State of Illinois comprise the same or partly the same territory, the municipalities concerned have the power jointly to purchase land and to construct buildings and all necessary appurtenances within their common corporate limits, and to own, operate, and maintain the land and buildings jointly with one another, for their joint municipal purposes, on terms and conditions to be agreed upon by the municipalities. Such municipalities have the power to exercise the right of eminent domain by condemnation proceedings in conformity with the provisions of the constitution and statutes of the state for the acquirement of property, advantageous or desirable for joint municipal purposes.
65 ILCS 5/11-69-1