Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 143. This guidebook was prepared for a field trip to be conducted prior to the commencement of the 28th International Geological Congress, convened in Washington, DC, July 1989. The purpose of this field trip is to examine the geologic factors that controlled the deposition of Carboniferous rocks in the Illinois and Appalachian basins, with emphasis being placed on basinal tectonic evolution, sedimentation, and paleoclimate. Throughout the trip, lithostratigraphic and biostratigraphic correlations between the Illinois and Appalachian basins will be stressed in order to provide continuity between the two areas. In addition to this, geochemical conditions of sedimentation and peat formation will be illustrated and discussed on the basis of the stratigraphic and regional distribution of chemical sediments, including coal beds. The important Mississippian/Pennsylvanian (mid-Carboniferous) boundary, and the sedimentological, paleobotanical and paleoclimatic changes associated with it, will also be emphasized.