The tallgrass prairie was once an extensive ecosystem that spanned most of Illinois. Given the state’s lack of topographic relief, this expansive habitat appeared as a “sea of grasses” that extended to the horizon. On closer examination, this seemingly uniform and unvarying landscape was made up of a patchwork of different habitats, each supporting a different suite of species, making the prairies a biologically diverse ecosystem. One important driver of this diversity was the mosaic of soil and bedrock underlying the prairies. For example, the xeric (dry) communities of the prairies were associated with exposed bedrock (dolomites, alvars), glacial deposits (hills) or sandy soil that had little water retention capacity. As these were often more stressful environments, these areas supported only a few specialized species, creating unique plant communities, which included a number of important endemic and rare species. With landscape fragmentation, these habitats are becoming increasingly isolated, and many populations are declining and exhibiting reproductive failure. To slow the decline of this regionally important species, we propose to identify demographic, genetic, and management-related drivers of population decline. Recommendations will be developed based on findings and past data to ensure that land managers have clear guidance for how to support healthy populations of rare species. (Fant, Kramer, POC, Casanova-Urbana, Zeldin).