Double-crested Cormorants (Phalacrocorax auritus) were not observed breeding in the inner coast of Washington and British Columbia until the 1920s and 1930s, whether the breeding was either a re-colonizing event or a new expansion was unknown. Archaeological evidence from Watmough Bay, a shell midden site on Lopez Island, San Juan Islands (Washington State), was analyzed to place the recent changes in breeding distribution in deeper historical context. The Watmough Bay faunal assemblage contains large numbers (n = 2,397) of cormorant bones. Of those specimens that could be identified to species (n = 358), 99.7% were identified as Double-crested Cormorants. The majority (97%, n = 2,336) of the cormorant remains are from juveniles or chicks, which were collected while still at the colony. Radiocarbon dating indicates the majority of the site accumulated between AD 300– 600. Evidence for a ca. 1,500-year-old Double-crested Cormorant colony near Lopez Island confirms that the species did breed in the region prior to the early 20th century. The study further documents the value of archaeological data for current wildlife management.