The monarch butterfly Danaus plexippus is a textbook example of a toxic animal with aposematic coloration, but we know little about how anthropogenic stressors may affect their chemical defense (cardenolides) or wing color. Given the interest in using roadside habitat to conserve monarchs and pollinators, we chose sodium as a representative anthropogenic stressor since it is often elevated along roads due to application of deicing salt. We reared monarch caterpillars through adulthood on common milkweed Asclepias syriaca watered with a salt solution to mimic sodium levels commonly found along roads in Minnesota, USA. We quantified the concentration and relative polarity of cardenolides in milkweed and in the wings of 100 female monarchs using HPLC. We also measured the hue, saturation, and brightness of an orange section on the forewings of 100 male and female monarchs. Preliminary results show no significant difference in total cardenolide concentration between control and treatment milkweed or monarchs. However, we found differences in the concentrations of specific cardenolides sequestered by monarchs in the two groups – monarchs fed salted milkweed had higher concentrations of more non-polar cardenolides, which are typically more toxic than polar cardenolides. While the fitness impacts of this change are unclear, these results emphasize the importance of considering all aspects of an organism’s biology when making conservation decisions.