Alcatraz Island, referred to colloquially as ""the Rock,"" was converted from a military stockade to a federal maximum security prison in the 1930's to house some of America's most dangerous criminals. Alcatraz was supposedly inescapable, but in 1962 three inmates would stage a daring escape attempt that continues to impress experts to this day. Tune in when The UnXplained returns this Saturday, July 11th at 9/8c to learn more about Alcatraz and some of history's greatest escapes. | HISTORY

963K views · 11K reactions | Prisoner Who Escaped From Alcatraz Sends Letter To The FBI 50 Years Later! Was Alcatraz, San Francisco’s notoriously inescapable prison, invulnerable to such escape attempts? Well, one letter – claiming to be from someone who successfully escaped the prison – threatens to shatter this idea. Let’s dive into the San Francisco bay and try to get to the bottom of it. | Be Amazed | Facebook