Color polymorphism is the presence of multiple color phenotypes (i.e., morphs) that co-exist within populations. The Eastern Red-Backed Salamander, Plethodon cinereus, has two common color morphs, a ‘striped’ morph exhibiting a red stripe on a black back, and an ‘unstriped’ morph that is completely black. Previous studies on P. cinereus detected a correlation between temperature and morph frequencies, along with other physiological and behavioral differences. However, previous studies have largely focused on a single population at a single time point, and therefore, spatiotemporal patterns of this polymorphism remain unknown. We examine whether morphs respond to changes in climate through differential alterations in body size and/or changes in morph frequency ratios across multiple populations and decades. We collected data from the Smithsonian National Museum of Natural History by taking digital photographs of 2,902 salamanders from five populations. Salamander length was measured, and citizen scientists identified color morph from photographs. Mixed-models show that smaller individuals are found in warmer temperatures and seasons, and salamander body size is decreasing over time. Models also show that the proportion of striped morphs has increased over time, and that striped morphs are more associated with warmer temperatures, while unstriped morphs are more associated with higher precipitation.