Little information is available on the extent of local adaptation for many native grass species. This is the case for squirreltail (Elymus section Sitanion), despite this group's prevalence and importance in rangeland restoration efforts. I evaluated 32 populations of E. elymoides ssp. brevifolius race C, a phylogenetic subdivision of bottlebrush squirreltail (E. elymoides) centered in the northern Intermountain West, for phenotypic variables and neutral genetic markers to measure their association with geographical origin. Phenotypic traits were measured in common field and greenhouse environments, and genetic diversity was assessed using Amplified Fragment Length Polymorphism. Three factors were extracted from the phenotypic data set using common factor analysis. Factor 1 explained 37.7% of the variation among all of the variables; it had positive factor loadings for phenology (late maturity), biomass, and leaf area index, negative loadings for leaf area and root length, and was negatively correlated with elevation (r = -0.71). Factor 2 explained 14.5% of the variation among all of the variables; it had positive factor loadings for plant height and leaf number per tiller, negative loadings for seed yield and tiller number, and was positively correlated with longitude (r = 0.54) and average annual minimum temperature (r = 0.39). Factor 3 explained 12.8% of the variation among all of the variables; it had highly positive factor loadings for specific root length and specific leaf area, negative loadings for canopy height and mass per tiller. Correlations among phenotypic, environmental, genotypic, and geographic-origin distances were positive (r = 0.723-0.900), which suggests that ecotypic variation is an important feature of this group. This information, in conjunction with previously established Level III ecoregions, was used to delineate four adaptive zones for race C.