Andropogon gerardii (Big Bluestem) is a dominant grass of the North American tallgrass prairie. It is also found in remnant populations in the eastern United States, including North and South Carolina, often in association with other species with prairie affinities. We characterized eight A. gerardii population sites across various physiographic regions of North and South Carolina. A total of 362 quadrats (1 m × 1 m) were sampled during the 2006–2008 growing seasons for species occurrence and site and quadrat frequency. Associated species were assigned a commonness index (CI). A Sørensen's Community Coefficient was used to determine floristic similarities among the sites. In addition, soil samples in three quadrats were sampled at each site at three depths (0–10 cm, 11–20 cm, and 21–30 cm) and analyzed for pH; organic C and N contents; extractable P, K, Ca, Mg, Zn, Mn; and CEC (cation exchange capacity). A total of 306 vascular plant species was identified comprising 64 families, including 99 (32%) graminoids. There were 61 (20%) Poaceae and 63 (20%) Asteraceae. Species per quadrat ranged from 1 to 13 with a mean of 5. Andropogon gerardii had the highest CI value (5900), followed by Rubus spp. (1260). Community Coefficient values were < 0.5 for all pairings between sites, indicating high divergence in species composition among even nearby sites. There were 14 rare or watch-listed species identified, including the federal endangered Helianthus schweinitzii at Troy Prairie. A total of 153 (50%) of the species had been previously described as occurring in prairie-like associations. Soil pH values varied from 4.8 to 6.9 among the sites and depths. Ca and Mg nutrient values were also highly variable. Andropogon gerardii was found at high frequencies across all sites, indicating its broad tolerance for a variety of edaphic conditions.