Illinois Soil Surveys

Illinois has 102 USDA soil survey areas covering a wide range of landscapes and soil conditions. The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil, making up roughly 54% of surveyed soils. Mollisols — grassland soils with a thick, dark, fertile topsoil rich in organic matter account for another 31%.

In terms of drainage, 31% of Illinois soils are classified as somewhat poorly drained. About 56% of soils have some form of poor drainage, which is important to consider for septic systems and foundations. Drainage class affects everything from septic system design to basement feasibility to garden planning. Use the survey area pages below to see drainage details for specific counties, or look up any address for an exact soil profile.