A disjunct stand of Andropogon hallii Hack. from Bureau County, Illinois is described. Based on sessile awn length, and length and number of rachis hairs, this population is morphologically distinct from local A. gerardii Vitman. The two species of Andropogon are somewhat separated ecologically. We believe A. hallii may be relic from the xerothermic period when the species may have been more abundant in the Midwest. Descriptions of locality, associated plants, soils and species characteristics are included and discussed.