It is unclear how the environmental heterogeneity of the prairie biome of North America contributes to the biogeographic ranges of vascular plant species, particularly herbaceous taxa. We examined the spatial distributions of 30 abundant plant species of the grasslands of North America distributed among four functional groups: C 4 grasses, C 3 grasses, forbs, and woody species. For each species, we mapped its distribution using occurrence data from georeferenced herbarium specimens and a species distribution model (MAXENT). We then assessed which of several climate, soil, and elevation variables contribute to determining its range. On average, these 30 plant species are distributed over large areas, with an average range size of 1,989,750 km 2 . Temperature variables contribute the most to the MAXENT model for 27 of the 30 species. Size of range, abruptness of boundary edges, and location of range vary among all 30 species. Functional groups differ primarily in range size and the centroid of the ranges. Conservation of tallgrass, mixed-grass, and shortgrass prairie biomes will require a flexible strategy with widely distributed habitat over the Great Plains along both north-south and east-west gradients. [