Humboldt Bay National Wildlife Refuge Complex (Complex), which includes Humboldt Bay National Wildlife Refuge (NWR) and Castle Rock NWR, is located on the northern coast of California. Humboldt Bay NWR is located in the vicinity of Eureka and Arcata with refuge units distributed around Humboldt Bay, the largest bay between San Francisco Bay and Coos Bay, Oregon. In 1971, Humboldt Bay NWR was established to conserve coastal habitats for a great diversity of animals and plants, especially migratory birds. Years later Humboldt Bay NWR added the Lanphere and Male'l Dunes Units to help conserve the most pristine remaining dune ecosystem on the west coast of the United States.