ABSTRACT From 2004 to 2012 a study of the flora and floral communities at Cabin Creek Raised Bog (Cabin Creek) was conducted. Cabin Creek, designated a National Natural Landmark by the National Park Service in December, 1974, is privately owned. It is located in west-central Randolph County, Indiana. An inventory of the vascular flora revealed 478 taxa representing 282 genera and 91 families. The 12 families containing approximately 62% of the documented species (in order by number of species) were Asteraceae, Cyperaceae, Poaceae, Rosaceae, Liliaceae, Lamiaceae, Scrophulariaceae, Apiaceae, Fabaceae, Ranunculaceae, Brassicaceae, and Polygonaceae. Of the 478 documented species, 400 were native, 78 were exotics, and 118 represented new Randolph County records. There were three species with Indiana Rare-Threatened-Endangered status, including Veratrum virginicum (endangered), Triantha glutinosa (rare), and Melica nitens (threatened). A physiognomic analysis (i.e., summary of plant form or habit) is presented. The floristic quality index (FQI) for native species is 85.6 (78.3 for all species) and the mean coefficient of conservatism (mean C) for native species is 4.3 (3.6 for all species). These numbers clearly signify the ‘‘paramount importance’’ of the floral natural heritage of the approximately 7 ha Cabin Creek site and indicate that it is among the highest floristic quality sites in the state. The flora occurring in the major community types (wetland border/marshes, sedge meadow–calcareous fen complex, moist prairie, mesic to dry woodland, moist woodland and hardwood swamp) is described.