Alcatraz is part of the Golden Gate National Recreation Area, including Muir Woods and the Golden Gate Bridge. (Photos by Carla Babb and Ryan Newell)
The prison greeted approaching ships with a threat: "Persons procuring or concealing escape of prisoners are subject to prosecution and imprisonment."
The Rock sits about 2.5 kilometers away from San Francisco. Part of the Rock is closed each year from February to September for bird breeding season.
Before it was a prison, Alcatraz was known for housing the first lighthouse and US-built fort on the West Coast to protect San Francisco during the gold rush.