Greetings Ralph,
I can provide you the names of 20 different species capable of growing on “clay” soils, but that does not mean they will grow or grow well. Due to the great variability of Illinois soil texture, please contact your local Department of Natural Resources district forester http://dnr.state.il.us/conservation/forestry/DISTFRSTMAP.pdf to provide you with a list of suitable tree species based on the exact soil description, slope rating, and location (upland, floodplain, reclamation/spoil, urban, etc.) of the planting site. Upon providing your district forester with your legal property location, along with a legible aerial photograph of your property and tree planting locations, your district forester will be able to recommend the best native hardwoods for your planting site.
I realize this is not the initial answer you were looking for; however, it is the correct answer you need to properly address the concept of planting the correct tree on the "right" soil type, in the “right” location.
I hope this information was useful.
