Cape Mendocino, the western most point in California, juts out into the Pacific between Eureka and Fort Bragg. This prominent headland pushes into the California Current, creating upwelling and eddies that could collectively represent a barrier to the dispersal of marine larvae between populations to the north and south of it. Although Cape Mendocino is well known to mark a boundary between the Monterey and Mendocinian biogeographic provinces, little work has been done to investigate its role as a barrier to gene flow within species. This exploratory project asks whether there are detectable genetic differences between marine populations north and south of Cape Mendocino for a range of species including limpets, barnacles, and seastars. Finding such genetic structure could have implications for the management of California fisheries as well as shining new light on species diversification within the sea.