Alcatraz The name Alcatraz is derived from the Spanish "Alcatraces." In 1775, the Spanish explorer Juan Manuel de Ayala was the first to sail into what is now known as San Francisco Bay - his expedition mapped the bay, and named one of the three islands Alcatraces; over time, the name was Anglicized to Alcatraz. While the exact meaning is still debated, Alcatraz is usually defined as meaning "pelican" or "strange bird." In 1850, a presidential order set aside the island for possible use as a United States military reservation. The California Gold Rush, the resulting boom in the growth of San Francisco, and the need to protect San Francisco Ba