Distribution of Coal in Indiana (CO-08)
Our Indiana coalfields lie on the east edge of a broad, gently downwarped bedrock structure called the Illinois Basin (stippled area on map). Coal-bearing rocks are restricted to an area of about 6,500 square miles in southwestern Indiana because those that have existed elsewhere in Indiana have been removed by erosion.

Because of downwarping, the rocks dip to the southwest at 30 feet per mile, and each coalbed is at increasingly greater depth in that direction. The most active mining in Indiana has been in Vigo, Sullivan, Greene, Knox, Pike and Warrick Counties where the thicker and more widespread rocks of Middle Pennsylvanian age are near the surface. Most Hoosier cola is now strip mined, but vast resources of coal are available for underground mining.

Our Hoosier State Beneath Us: Coal