The federal penitentiary at Alcatraz Island, about a mile off San Francisco’s shore, was meant to be escape-proof. But that didn’t stop inmates from trying. In 1962, three prisoners staged what became one of the most notorious unsolved crimes in American history.

John Anglin, his brother Clarence Anglin, and Frank Morris, all bank robbers, spent months preparing their escape from Alcatraz. Using crude tools, including a drill crafted from a vacuum motor, they burrowed through the walls of their cells. Crucial to the plot: Alcatraz had implemented a music hour, during which inmates created a cacophony of instrumental sounds that drowned out the tunneling work.

On the night of June 11, 1962, the men wriggled into a utility corridor, clambered to the roof, slid down a pipe, and climbed two barbed wire fences to reach the water’s edge. There, they pushed off into the inky waters on a raft made of raincoats.

The next morning, papier-mâché heads with real hair were discovered in the men’s beds that had fooled guards during their nighttime checks. A sprawling manhunt turned up empty. The men were never seen again.

The F.B.I. acknowledged that the breakout was brilliant. Yet few believed the men could have survived the bay’s maelstrom of strong currents and frigid waters.

Even so, with no bodies or arrests, the possibility remained that Morris and the Anglins had escaped to freedom from the nation’s most forbidding maximum security prison, a fantasy memorialized by Clint Eastwood in “Escape from Alcatraz.” Deepening the mystery: flowers were said to arrive reliably on special occasions at the Anglins’ childhood home, and two men dressed as women were said to have attended the funeral of the brothers’ mother in 1973.

If the men survived, they would all be in their 90s today. Is it possible? Investigators continue to welcome leads. FBI.gov

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