More than half a century later, the thick roots of ficus trees stretch through the corridors and down uneven stone steps. The air is eerily still inside high walls that block the breeze.
Madeleine Calcagni, who runs the Royale inn and restaurant, stays away from St. Joseph: "I couldn't do business over there because people there suffered a lot, and you could feel it."
It's an odd business turning a prison into a tourist attraction. Visitors pose for photos gripping cell bars, close themselves in dark solitary cells and bask in the sun next to a pool built with forced labor.
"It's like a paradise, but it's strange to know that before it was a prison," said Audrey Bruyere, 23, a Paris student.
The islands teem with animals introduced by humans: Macaws screech overhead, squirrel monkeys hurtle between branches and large rodents known as agoutis scamper in the underbrush.
Tourists sip wine at the open-air restaurant overlooking Devil's Island, where prisoners spent years receiving their provisions along a cable that stretched across from Royale.
Perhaps the most famous of those on Devil's Island was Dreyfus, a Jew falsely accused of spying for the Germans and imprisoned alone from 1895 to 1899. The victim of a paroxysm of French Jew-hatred and an army too proud to admit its mistake, he was isolated in a small stone house, tormented by mosquitoes, hungry ants and loneliness.
"Impossible to sleep," he wrote in his diary the night of April 14, 1895. "This cage, in front of which the watchman walks like a phantom that appears in my dreams, the itch of all the beasts that run across my skin, the anger that roars in my heart."
He eventually returned to France when evidence pointed to another officer, and he was exonerated. His tiny house of raw stone still stands near the southern tip of Devil's Island.
His case brought infamy to the island, and its name became synonymous with the horrors of the penal colony. But the prison continued to function until public opinion finally forced its closing.
At least five prisoners escaped from the islands, one using a canoe in 1921 and four using a stolen steam ship in 1944, historian Eugene Epailly said. Others died or were arrested trying to escape. Most didn't dare brave the sea, Epailly says. "The sharks were the best guards."
Associated Press writer Brian Rohan in Paris contributed to this story.