Located on an island in San Francisco Bay, Alcatraz was once considered one of the country’s most secure prisons. But that didn’t stop three prisoners from making a daring escape the night of June 11, 1962. They set sail across the bay on a homemade raft made of raincoats. Then they vanished. What happened to them? Explore the theories and discover why their escape has become one of history’s greatest mysteries. Part of the History's Mysteries series.