Referred to as The Rock, this small island just off the coast of San Francisco was first developed with its facilities as a lighthouse, military fortification and a prison at later stages. Due to its isolation from the outside by the cold, strong, hazardous currents of the waters of San Francisco Bay, Alcatraz was used to house prisoners from as early as 1861. Some of the notable criminals that spent time on Alcatraz are Al Capone, Robert Franklin Stroud and George “Machine Gun” Kelly.
In my personal opinion, this place is overrated and over sold. Although a must see for all it represents, I think they market it quite well to maintain a mystery around it. It is definitely a place you want to visit and see, but you will probably not want to go there again. You can see the whole island using the audio guide in less than 3 hours no matter how much time you try to waste.