The isolated Kalaupapa region, Moloka‘i Island, Hawai‘i, offers archaeologists and ecologists a unique opportunity to study traditional Hawaiian limpet (‘opihi) (Cellana spp.) harvesting from the Proto-Historic Period (1650–1795), Early Historic Period (1795–1866), and the present day. In this study, archaeological collections, modern harvests, and field observations are used to describe a regular pattern of slightly larger mean limpet size in western shoreline harvests and an increase in average limpet size from the Proto-Historic Period to the present. Although further investigations are necessary to test alternative explanations, these results suggest (1) that shelter from ocean currents and trade winds may provide a microenvironment favorable to local limpet growth, and (2) a lessening of harvesting pressure concurrent with the massive depopulation of the study area after European contact. Future studies should focus on identifying possible ecological factors impacting average size, documenting changes in limpet size using specimens from archaeological deposits, and accounting for the impact of population change on marine resources in historic and prehistoric Hawai‘i.