Seeing that Illinois is currently without a forest products utilization and marketing specialist, I'll try to provide as much information as I can.
For a list of licensed timber buyers in the state of Illinois, please refer to the following Web site: http://dnr.state.il.us/admin/systems/Pdfs/TimberBuyers.pdf
For a list of Illinois Sawmills: http://dnr.state.il.us/conservation/forestry/05/sawmills2005.pdf
For a list of Illinois Timber Prices: http://web.extension.uiuc.edu/forestry/il_timber_prices/index.html
Web site and Contacts of Illinois Wood Products Association: http://www.illinoiswoodproducts.org
Dr. John Phelps is the Illinois Wood Products Association executive director (firstname.lastname@example.org)
I wish I could provide more information, but Illinois has been without a forest products specialist for over 7 years, which is truly unfortunate. My suggestion is to get in contact with the Illinois Wood Products Association for further assistance.
Best of luck to you and your business!