Rock asphalt or lithified oil sand and heavy oil occurring in Mississippian and Pennsylvanian (Carboniferous) strata along the southern and southeastern edges of the Illinois Basin in Kentucky are of increasing interest in the early 21st century. An impetus for renewed interest in asphaltic materials as well as heavy oils and potentially conventional oil located in south-central Kentucky is understandable, considering an overall increase in product price and technological advances in proposed recovery methods. Discussion in this chapter focuses on the regional structural setting, geographic and stratigraphic distribution of heavy oil and asphalt rock, proposed source rocks, general migration pathways, reservoir rock characteristics, and properties of the hydrocarbon resource. Additionally reviewed are the storied history of heavy-end hydrocarbon extraction, a series of projects and ongoing development of unconventional resources, and the potential for refining these resources.