If a petition under Section 10 is filed with the clerk of a township and the proposed district boundaries do not extend beyond the boundaries of the township, the township may form or renew the district without an intergovernmental agreement with the county in which the township lies, but the township must enter into an intergovernmental agreement with any municipality that has territory within the township.
If a petition under Section 10 is filed with the clerk of a county and the proposed district boundaries are solely within the county, the county may form or renew the district without an intergovernmental agreement with any municipalities or townships with territory within the county. If a petition under Section 10 is filed with the clerk of a county and the proposed district boundaries includes portions of another county, the county in which the petition was filed must only enter into an intergovernmental agreement with the county or counties in which the other territory is situated in order to form or renew a district.
70 ILCS 3455/20