Until about ten thousand years ago, Angel Island was connected to the mainland; it was cut off by the rise in sea levels due to the end of the last ice age. From about two thousand years ago the island was a fishing and hunting site for Coast Miwok Native Americans. Similar evidence of Native American settlement is found on the nearby mainland of the Tiburon Peninsula upon Ring Mountain. In 1775, the Spanish naval vessel San Carlos made the first European entry to the San Francisco Bay under the command of Juan de Ayala. Ayala anchored off Angel Island, and gave it its modern name (Isla de los Angeles); the bay where he anchored is now known as Ayala Cove.
Like much of the California coast, Angel Island was subsequently used for cattle ranching. In 1863, during the American Civil War, the U.S. Army established a camp on the island (now known as Camp Reynolds or the West Garrison), and it subsequently became an infantry garrison during the US campaigns against Native American peoples in the West.
Fort McDowell
In the later 19th century, the army designated the entire island as "Fort McDowell" and developed further facilities there, including what is now called the East Garrison or Camp McDowell. A quarantine station was opened in Ayala Cove (which at the time was known as Hospital Cove) in 1891. During the Spanish�American War the island served as a discharge depot for returning troops. It continued to serve as a transit station throughout the first half of the 20th century, with troops engaged in World War I embarking and returning there.
During World War II the need for troops in the Pacific far exceeded prior needs. The facilities on Angel Island were expanded and further processing was done at Fort Mason in San Francisco. Prior to the war the infrastructure had been expanded including building the Army ferry General Frank M. Coxe, which transported troops to and from Angel Island on a regular schedule.
