This professional paper is the fifth in a series of paleotectonic studies each covering a geologic system in the conterminous United States. Part I provides a region-by-region discussion of data concerning the Mississippian System and an explanation and documentation for the maps and sections contained in part III. Part II of the paper provides a summary of the Mississippian System, presents interregional interpretations permitted by this study, and includes sections on notable features of the system. The maps contained in the separate case as part III may be divided into two groups: (1) a sequence of factual or basic maps that shows, with a minimum of interpretation, the Mississippian System as it occurs today, and (2) interpretive maps that attempt a reasonable reconstruction of the original extent of the system, its tectonics, environment, and geography.