I wasn't even aware that Alcatraz Island is a unit of the National Park Service. Some tips for visiting...

Alcatraz does not charge any entry fee, but the only way to get there is via private ferry service:

http://www.alcatrazcruises.com/

So then are we free to wander The Rock by ourselves?

Or do we have to go with a tour?

In theory you can wander by yourself. In practice it's hard to avoid being herded into an audiotour for about half of the time.

It seems like most of the visitors to Alcatraz are interested in escapes from the federal penitentiary.  I heard several questions which weren't answered on our tour but I learned more about later.

* How many people tried to escape, and what happened to them?

36 prisoners tried to escape in 14 attempts (2 of them tried twice, so actually there were only 34 individuals).  Shot and killed during escape: 7 Executed for committing murder during escape attempt: 2 Presumed drowned: 5 Recaptured: 18 Snuck back into prison: 1 Possible escape: 3

Full breakdown:

Bowers shot; Cole drowned; Roe drowned; Franklin shot; Limerick shot; Lucas recaptured; Barker shot; Martin recaptured; McCain recaptured; Young recaptured; Stamphill recaptured; Cretzer recaptured; Shockley recaptured; Kyle recaptured; Barkdoll recaptured; Bayless recaptured; Boarman drowned (after being shot, but he's listed as presumed drowned); Brest recaptured; Hunter recaptured; Hamilton snuck back; Walters recaptured; Giles recaptured; Carnes recaptured; Coy shot; Cretzer shot; Hubbard shot; Shockley executed; Thompson executed; Wilson recaptured; Burgett drowned (only body recovered after presumed drowning); Johnson drowned; Morris escape?; J Anglin escape?; C Anglin escape?; Parker recaptured; Scott recaptured

* Did prisoners try to escape by sneaking onto the boat?

Only one prisoner (John Giles) seems to have tried it, and the main barrier to his attempt was getting a full Army uniform.  He made it to Angel Island but was recaptured there.

* Why do people consider the Morris/Anglin escape to have possibly been successful, unlike other escapees who went into the water?

The Morris/Anglin escape attempt is unique in using a full-on raft.  The water in San Francisco Bay is so cold, and the tides are so strong, that swimming or using a personal flotation device was always fatal after about 1 hour.  Remains of the raft, along with paddles and personal items, were found on Angel Island soon after the escape.

* The Morris/Anglin attempt used a drill made with a vacuum cleaner motor.  How could something that loud have been deployed without detection?

Evidently the drill was fired up only during the nightly music hour, when Morris would play the accordion. During the escape they employed a concertina to inflate their raft.

It's hard to get a feel for how hard it is to leave the island, until you're on the island.

The water is really cold -- 54 degrees -- and if a person stays in that water for 50 minutes there's only a 50% chance of survival.