A study of the McCourt Sandstone Tongue and the Glades coal bed of the Upper Cretaceous Rock Springs Formation in the Rock Springs coal field has provided valuable data for reconstructing an ancient coal-forming depositional environment. The sandstone and coal were deposited on a strand plain along the western shores of the Late Cretaceous interior seaway of North America. The McCourt Sandstone Tongue consists of a sequence of lenticular, eastward offtapping, north-northeast-trending, quartzose sandstone shoreline deposits. Lithofacies include lower and middle shoreface, surf, and forebeach, which are well preserved and are identifiable by their color, stratigraphic position, and sedimentary structures. The Glades coal bed formed in a narrow lagoon between two of the offlapping strand plain sandstones. Sedimentologic, palynologic, and maceral studies reveal that the coal was derived from organic debris that accumulated on the floor of a forest swamp that originally occupied the center of the lagoon and later expanded across the lagoon. The forest swamp was surrounded by a reed swamp. Landward of the reed swamp was an apron of sand that resulted from infilling of the western margin of the lagoon by detritus eroded from an older, abandoned strand-plain shoreline deposit. Initially, a large, open body of brackish water was situated at the eastern margin of the lagoon. The Snuggedy Swamp of the lower coastal plain of South Carolina is considered a modern analog of the depositional setting of the Glades coal bed.