We measured grasshopper densities on 66 shortgrass, mixed grass, tallgrass and hayfield plots on Boulder, Colorado, open space in 1995–1996. Grasshoppers as a group, and most species individually, were more abundant on relatively sparse short and mixed grass plots than on lusher hayfields and tallgrass plots—a result consistent with the hypothesis that most species require warm and sunny open ground for survival and reproduction. Bandwinged grasshoppers (Oedipodinae) were particularly associated with open ground in shortgrass vegetation, whereas spur-throated grasshoppers (Melanoplinae) were most abundant in mixed grass plots with a high percentage of forb vs. graminoid cover. Slant-faced grasshoppers (Gomphocerinae) were the most uniformly distributed among habitats, but were generally associated with plots including relatively high proportions of grass vs. forb cover. While 20 of the 25 most common grasshopper species on Boulder open space occurred in all four grassland types, each habitat was dominated by a distinctive set of species. However, numerically dominant grasshoppers on short, mixed and tallgrass plots only loosely resembled groups of dominant species in the same habitats elsewhere on the Great Plains. While most Great Plains grasshoppers are widely distributed, they are apparently numerically responsive to combinations of environmental conditions expressed at local scales. Common species of grasshoppers on Boulder open space in 1995–1996 were the same as those collected in the region in the 1950s. Our results suggest these protected grasslands, although invaded by alien vegetation and fragmented by suburbanization, are still effectively conserving this particular insect group.