Illinois Geologic Quadrangles (IGQs) depict Illinois geology at a 7.5 minute quadrangle scale. The compilation of these digital data products was funded by the the US Geological Survey () via the National Cooperative Geologic Mapping Program. Some of the original mapping was also funded by the Illinois Geologic Mapping Program. A list of is available from the Illinois State Geological Survey (ISGS).
IGQ Digital Data Products are .zip files which contain digital components of IGQ hard-copy maps. These maps address such geologic themes as surficial geology, bedrock geology, bedrock topography, glacial drift thickness, and aquifer sensitivity to contamination. IGQ Digital Data Products are available for the Alton, Elburn, Elsah, Geneva, Grafton, and Villa Grove Quadrangles in Illinois.
The Alton Surficial Geology IGQ Expanded Digital Data Product is available for download free-of-charge as a product sample.