Humboldt Bay is a natural bay and a multi-basin, bar-built coastal lagoon located on the rugged North Coast of California, entirely within Humboldt County. It is the largest protected body of water on the West Coast between San Francisco Bay and Puget Sound, the second largest enclosed bay in California, and the largest port between San Francisco and Coos Bay, Oregon. The largest city adjoining the bay is the regional center and county seat of Eureka, followed by the college town of Arcata. These primary cities together with adjoining unincorporated communities and several small towns comprise a Humboldt Bay Area total population of nearly 80,000 people, which accounts for nearly 60% of the population of Humboldt County. In addition to being home to more than 100 plant species, 300 invertebrate species, 100 fish species, and 200 bird species, the bay and its complex system of marshes and grasses support hundreds of thousands of migrating and local shore birds.