Do be aware that at that time it may not have been legally required to need a court order to change a name. If you refer to the Wikipedia article on "Name change," as of 2009, a person could legally change their name without paperwork by usage alone in 46 states. However, some financial institutes or government institutions do require evidence of a court order to make a change.
If there was a court order recognizing a name change, it is likely with a state court. You can find some information about what state courts were in place over time on the Illinois Courtspage of FamilySearch's wiki.
We hope this is helpful. Best of luck with your research!
