Greetings Dave,
Most landowners in Illinois plant what we call "woods run" variety of black walnut, i.e., non-genetically improved populations available for purchase by most private nurseries or available from the Illinois Dept. of Natural Resources nursery system. Unless you have premier black walnut growing sites, soils, and conditions (i.e., deep, moist, well drained soils), I would suggest going with standard “woods run” varieties.
However, Purdue University has a black walnut breeding program (http://www.agriculture.purdue.edu//fnr/). Furthermore, Hensler Nursery out of Hamlet, Indiana, offers “Pence Select” superior black walnut stock. Purdue and Pence Select black walnut seedlings are not genetically modified, but “selected” for superior growth, form, and anthracnose resistance.
This should get you started!