The San Francisco Bay is the largest estuary in the Americas, covering 1,600 square miles including its smaller estuaries, wetlands, etc. They bay was formed when a tectonic shift caused Lake Corcoran to spill into the central valley, forming canyons at the northern part of the bay. The rise in the sea level at the end of the last ice age filled the valley, creating the geology we see today.
The Ohlone people inhabited the area from 15,000 years ago to 10,000 years ago, before they were displaced by the rising sea level and the creation of the bay. Gaspar de Portola was the first recorded European to discover the bay in 1769, and the first to enter it, passing through the Golden Gate in 1775, was Juan de Ayala.
After the United States defeated Mexico in the Mexican-American War, the United States seized the region in 1848. During the California Gold Rush, the San Francisco Bay emerged as the dominant shipping seaport on the West Coast.
The Martin Luther King Jr. Regional Shoreline is a 741-acre regional park near the Oakland Airport on the San Leandro Bay. The park was established in 1993. Within the park are the 50-acre Arrowhead Marsh, a Western Hemisphere Shorebird Reserve Network protecting migratory birds stopping to rest on the Pacific Flyway. Over 90 bird species inhabit this area, including endangered species such as California Least Terns.