The most important mineral resource in Sullivan County has been coal, and for many years the county was one of the most important coal-producing areas in Indiana. The value of the total product of the mines in Sullivan County has reached billions of dollars (at current prices), and mining is still being done. Mining has affected the lives of all citizens of the county, whether or not they are directly involved in mining coal. This is the second county report on coal mining published by the Indiana Geological Survey. (Special Report 34 on Vigo County was the first.) Although it is primarily concerned with coal geology, other aspects of the industry are also treated, including historical developments, engineering problems encountered in mining, environmental problems produced by past mining, and speculations concerning the possible course of future events. A summary of the chemical characteristics of coal seams is also included. It is hoped that this report will interest a wide audience, not only coal geologists but also residents of Sullivan County, land-use planners and government officials, and the coal industry. Besides presenting maps and data relating to past developments and the current status of the coal industry, this report attempts to familiarize the reader with the types of information available from the Indiana Geological Survey and the possible uses and limitations of this information. Providing an overview of the coal industry in the county has been emphasized, but persons wishing information on coal resources in particular areas may also find the report useful. Readers requiring more detailed information for their own interpretations can contact the Indiana Geological Survey to obtain original sources of data.