Three Men Escaped Alcatraz on a Raft Made of Raincoats. They Were Never Seen Again.

At about 7 a.m. on June 12, 1962, a guard at Alcatraz Federal Penitentiary walked along a cellblock for the morning count.

In one cell, an inmate was still in bed. The guard called to him. He didn't move.

The guard reached through the bars and touched his head. It rolled off the pillow and fell to the floor.

It was a dummy. A head made of soap, toilet paper and plaster, painted to look like skin, with real human hair.

Three men were gone. They were never seen again.

The Rock

Alcatraz was the most famous prison in America. It sat on a rocky island in San Francisco Bay, about 2 kilometers from the city, and held men considered too dangerous or too likely to escape from other federal prisons.

The water around it is cold, often around 10 to 15 degrees Celsius, with strong currents. Officials said escape was impossible.

Over the prison's 29 years, 36 men tried in 14 separate attempts. Most were caught or killed. A few were never found.

The most famous attempt began in late 1961.

Four men

Frank Morris was serving time for bank robbery. He had escaped from other prisons before, and he was considered very intelligent.

John and Clarence Anglin were brothers from Georgia, also in prison for bank robbery. They had known Morris from an earlier prison.

Allen West, a car thief, had cells near theirs. All four were in neighboring cells in cellblock B.

Over about six months, they planned their way out.

The vents

Beneath the sink in each cell was a small air vent leading to an unguarded utility corridor behind the cells.

The concrete around the vents was old and damp from sea air. The men chipped at it with spoons taken from the dining hall, metal blades and a homemade drill powered by the motor of a stolen vacuum cleaner.

To hide the noise, Morris played an accordion during the prison's music hour.

To hide the holes, they covered them with painted cardboard and pieces of metal that looked like the original grilles.

Once through, they climbed up the pipes in the utility corridor to an empty space on top of the cellblock, which became their secret workshop.

The workshop

On top of the cellblock, hidden from the guards, the men built what they needed.

They stitched together more than 50 raincoats, taken from other inmates or the prison, into a raft about 1.8 by 4.3 meters. They sealed the seams using heat from the prison's steam pipes.

They made life vests from more raincoats, following a design in a magazine, Popular Mechanics.

They made wooden paddles. They turned a musical instrument, a concertina, into a pump to inflate the raft.

In their cells, they made the dummy heads, using a paste of soap, toilet paper and cement dust, painted with paint from the prison workshop, and topped with real hair collected from the prison barbershop.

June 11, 1962

On the night of June 11, the men put their dummy heads in their beds, crawled through their vents and climbed to the roof.

Allen West could not get out. The cement he had used to hold his fake grille in place had hardened, and by the time he broke free, the others were gone. He stayed behind and later told investigators the plan.

Morris and the Anglins crossed the roof, climbed down a pipe on the side of the building, crossed two fences and reached the northeast shore of the island. At about 10 p.m., they inflated the raft and pushed off into the bay.

Their plan, according to West, was to reach Angel Island, about 3 kilometers north, and then cross to the mainland, steal clothes and a car and disappear.

The search

The escape was not discovered until the morning count, nine hours later.

A huge search followed. Over the next days, searchers found a paddle near Angel Island, and life vests and pieces of raincoat material in the water and along the shore.

They also found a waterproof package containing photographs and the names and addresses of people the Anglins knew.

No bodies were ever found.

Drowned, or free?

In 1979, after a 17-year investigation, the FBI closed its case. It concluded that the men most likely drowned in the cold water, and that their bodies were carried out to sea.

The U.S. Marshals Service, which tracks escaped federal prisoners, kept the case open. The three men are still listed as wanted.

Over the years, there have been claims they survived. The Anglin family has said the brothers sent messages to their mother. In 2015, relatives released a photo said to show the two brothers on a farm in Brazil in 1975. Experts could not confirm who was in it.

In 2013, the San Francisco police received a letter claiming to be from John Anglin, saying all three had survived but that Morris and Clarence had since died. The FBI said its tests on the letter were inconclusive.

In 2014, scientists in the Netherlands used a computer model of the bay's tides. They found that a raft launched at around 11:30 p.m. could have been carried toward land north of the Golden Gate Bridge, but that later departures would have been far less likely to make it. The prison's records suggest the men may have left earlier, at around 10 p.m., which leaves the question open.

Alcatraz closed as a prison less than a year after the escape, in March 1963, mostly because it was too expensive to run.

What we still don't know

Did the men drown in the bay that night, or did they reach the shore?

If they survived, how did three of the most wanted men in America stay hidden for the rest of their lives?

Who wrote the 2013 letter?

And if they did make it, the U.S. Marshals would still like to hear from them.