Many studies have demonstrated plant response to warming temperatures, both as advancement in the timing of phenological events and in range shifts. Mountain gradients are ideal laboratories for studying species range changes. In this study of 363 plant species in bloom collected in five segments across a 1200 m (4158 ft) elevation gradient, we look for changes in species flowering ranges over a 20-year period. Ninety-three species (25.6%) exhibited a significant change in the elevation at which they flowered from the first half to the second half of the record, with many of these changes occurring at higher elevations. Most of the species exhibiting the changes were perennial plants. Interestingly, though many changes in flowering range were specific to higher elevations, range changes occurred all across the gradient. The changes reported in this study are concurrent with significant increases in summer temperatures across the region and are consistent with observed changes around the globe.