Alcatraz Island has loomed large in the American consciousness for nearly a century as a brutal prison full of notorious criminals from which escape is nearly impossible.

The San Francisco island fortress nicknamed “the Rock” served as a federal prison from 1934 until it shuttered in 1963 because of the staggering costs of operations and maintenance. In those nearly three decades, the isolated facility established a reputation for housing some of the most legendary convicts of the day, including gangsters like George “Machine Gun” Kelly and Al Capone.

Today’s Alcatraz is a tourist attraction, but President Donald Trump on Sunday said that he was ordering that the decommissioned prison be rebuilt and expanded to house the country’s “most ruthless and violent” offenders.

“When we were a more serious Nation, in times past, we did not hesitate to lock up the most dangerous criminals, and keep them far away from anyone they could harm,” Trump wrote on social media.

President Millard Fillmore set his sights on the island in 1850, envisioning the rocky terrain roughly a mile from the San Francisco coast as the ideal spot for a West Coast military installation. Fortified with more than 100 cannons, Alcatraz became part of a “triangle of defense,” along with Fort Point, near the southern entrance of what would become the Golden Gate Bridge, and Lime Point to the north, according to the Bureau of Prisons.

Four years later, Alcatraz became home to the first operational lighthouse on the West Coast, bolstering its role as a key lookout post for the San Francisco Bay.

Alcatraz later served as disciplinary housing for military detainees, and by the turn of the century it became a prison for Native Americans who refused to relinquish their children for forced reeducation. Nineteen members of the Hopi Tribe were sent to Alcatraz when they resisted the federal government’s assimilation program.

At the onset of World War I, conscientious objectors like anti-war activist Robert Simmons were imprisoned at Alcatraz as tales of the squalid living conditions reached the mainland. Simmons arrived at the facility in 1918 and was thrown into the “hole” for two weeks — described by the National Park Service as a “pitch-dark dungeon cell with slimy walls, crawling with rats.”

By the 1930s, the prison’s brutal conditions were being matched by its residents. Prisoners who couldn’t adapt to the rules of other federal penitentiaries — often killing and injuring other inmates or guards — were sent to Alcatraz. Mobsters like murderer Robert Franklin Stroud, known as the “Birdman of Alcatraz,” and mobster Whitey Bulger were among those who later served time on the Rock.

While Alcatraz became known for brutal conditions, its reputation was further enhanced by the common perception that it was inescapable. Getting past the prison walls was only one part of a perilous journey to freedom. Escapees also would have to swim more than a mile through frigid waters and powerful currents to reach the San Francisco shore. (Contrary to popular myth, there are no man-eating sharks in the bay, according to the Park Service.)

During the 29 years Alcatraz operated as a federal prison, 36 men attempted 14 separate escapes (including two inmates who tried twice), according to the Bureau of Prisons. The attempts ended with the prisoners’ capture, killing or drowning, including a 1946 escape attempt by six prisoners that left two guards dead and 18 injured in a two-day standoff that became known as the “Battle of Alcatraz.”

The fate of three Alcatraz escapees remains unknown. The Bureau of Prisons listed brothers John and Clarence Anglin and Frank Morris as “missing and presumed drowned” after a 1962 attempt, but their bodies were never found.

In 2018, a letter — first sent to San Francisco police in 2013 — surfaced in which the writer claimed to be John Anglin. The letter writer said that after he and the two other men escaped Alcatraz in June 1962, he was the only one still alive. A representative of the U.S. Marshals Service told The Washington Post at the time that the agency believed the letter was without merit.

Alcatraz ceased operations as a prison in 1963 when the factors that had made it so formidable also made it prohibitively expensive to operate: The facility needed $3 million to 5 million in restoration work, while the day-to-day operational costs per prisoner were more than three times that of a similar penitentiary in Atlanta.

Because of Alcatraz’s island location, necessities from food to fuel to water had to be brought from the mainland by barge each week.

Alcatraz Island was abandoned from the prison’s closure until 1969, when members of several Indigenous tribes occupied the island for 19 months, launching a new era of Indigenous activism that sought to pressure President Richard M. Nixon to repeal the federal policies known as “Termination and Relocation.”

After the occupation ended in 1971, the island and prison were turned over to the Park Service’s Golden Gate National Recreation Area in 1972. Alcatraz reopened to the public a year later as a tourist attraction.

The public’s fascination with Alcatraz kicked off a generation of films and books that sought to dramatize real events or use the prison’s legacy as a plot device. The 1979 film “Escape From Alcatraz” saw Clint Eastwood play Frank Morris as the ringleader of the 1962 escape. In the 1996 Nicolas Cage movie “The Rock,” a prisoner (played by Sean Connery) secretly known to be the only man to escape Alcatraz is recruited to help infiltrate the island and foil a terrorist plot.

In recent years, Alcatraz has drawn visitors who are more interested in its current residents than its past ones: the array of wild and cultivated flowers that bloom on the island.