Mining in the Illinois City Quadrangle
The mines in this quadrangle are un-named slopes and drifts in ravines. They are believed to have been operated as early as the Civil War, and the last one closed around 1940, but no operating names have survived. Consequently, it is not possible to know the production or the approximate undermined acreage.
The Rock Island Coal was the only seam mined. However, the lenticular and discontinuous coal, known locally as the Caseyville Coal (stratigraphically below the Rock Island Coal), may have been the seam mined in some cases, especially by low-volume short term local mines. Both coals undulate and vary considerably in thickness, thickening and thinning from both the top and the bottom of the seam.