Hello Mark, Black walnut is found in every county of the state. However, quality walnuts need deep, rich, well drained soils. These types of soils are often found in bottomland sites as long as the drainage is adequate. These soils can be found across the state, but are more restricted in some areas.
Upland soils are often less well suited, because of lower fertility or heavy clay components. Still, Illinois has upland sites that can grow good walnut.
You can check the soil suitability of any tract of land in Illinois using the Walnut Suitability ratings found on the Web Soil Survey (https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm). If you are unfamiliar with this software, you can ask your local Soil and Water Conservation Board employee, NRCS District Conservationists, or Extension Staff to help you locate the suitability ratings in your area.
