750 ILCS 5/104
The proceedings shall be had in the county where the plaintiff or defendant resides, except as otherwise provided herein, but process may be directed to any county in the State. Objection to venue is barred if not made within such time as the defendant's response is due. In no event shall venue be deemed jurisdictional.
In any case brought pursuant to this Act where neither the petitioner nor respondent resides in the county in which the initial pleading is filed, the petitioner shall file with the initial pleading a written motion, which shall be set for hearing and ruled upon before any other issue is taken up, advising that the forum selected is not one of proper venue and seeking an appropriate order from the court allowing a waiver of the venue requirements of this Section.
750 ILCS 5/104