President Trump said Sunday that he was ordering the FBI to reopen the Alcatraz Federal Penitentiary, the historic prison on an island off of San Francisco that has been closed since 1963.

“REBUILD, AND OPEN ALCATRAZ!” he wrote in a post on Truth Social. “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 in a post on Truth Social.

RELATED: If Trump really wants to reopen Alcatraz, he’ll have to go through California’s environmental laws

Once fortified with the goal of becoming the world’s most secure prison, the government closed Alcatraz because it was too expensive to run — costing three times as much as most other federal prisons.

Speaker Emerita Nancy Pelosi, in a statement posted Sunday to social media, said that Trump’s proposal “is not a serious one.”

“Alcatraz closed as a federal penitentiary more than sixty years ago,” she wrote. “It is now a very popular national park and major tourist attraction.”

The federal government would have some major challenges to overcome if it does want to make Alcatraz into an operating prison again, said local historian John Martini.

“It’s nowhere near a functioning island by any means,” said Martini, who has written about the military history of the San Francisco Bay. “God, it’s a wreck.”

The main prison has been deteriorating for years, save for some seismic upgrades that made it safe for visitors. Back in 1962, the Bureau of Prisons weighed making upgrades to the prison, but it would have cost $5 million — or $52 million today.

Were Trump to raze the existing structure and build anew, that too could be prohibitively expensive, Martini said. The island has no source of fresh water, which means that contractors have to ship their own water to make concrete.

The island is also a rock, with no soil to drill into. On top of that, there’s no electricity on the island, except what’s generated from a small system of solar panels. Many contractors operate on generators, so their fuel has to be brought over by boat. Bad sea conditions make it nearly “impossible” for them to land, too, Martini said.

“The reason it is not a prison now is because of the daunting challenges from six decades ago,” Martini said. “The idea that we’re going to forget all that and pick up where we left off during the JFK administration — let’s just say there will be a lot of challenges.”

The federal penitentiary opened in August 1934 and was in operation for less than 30 years. Inmates included notorious criminals such as Al Capone and George “Machine Gun” Kelly, who had a history of prior escapes from prison.

In 1962, three of Alcatraz’s prisoners escaped — John Anglin, his brother Clarence, and Frank Morris. They planted dummies in their beds, climbed out via rooftop ventilators, and launched a raft with the aim of crossing the Bay. They were never found and are believed not to have survived.

Who controls Alcatraz?

As of 1972, Alcatraz has been owned by the National Park Service. The Golden Gate National Recreation Area, which manages the island, did not immediately respond to a request for comment.

Can Trump really rebuild?

Alcatraz is on the National Register of Historic Places. If Trump is serious about rebuilding a prison on Alcatraz, it would likely have to remove its designation.

He could also end up getting held up by California’s strong environmental protection laws. Current contractors using heavy equipment must work around nesting sea birds, since the island is considered a protected environment, Martini said. Nearly a third of the island is closed much of the year so that Western gulls and cormorants can make their nests.

What’s on the island now?

Since 1973, Alcatraz has been open to the public, operating as a tourist destination and a museum looking back at its time as a federal penitentiary. The museum welcomes more than 1.4 million visitors each year.

The National Park Service has been in the midst of redesigning the museum and visitor experience, with the launch slated for later this summer, according to a social media post by the Golden Gate National Parks Conservancy Vice President Sean Kelley.

The annual Escape from Alcatraz Island is hosted on the island each year, which requires a 1.5-mile swim through the Bay’s choppy waters to the San Francisco shore.

The island is also popular with birdwatchers — it hosts over 20,000 birds, including murres, grebes and ducks.

Where do federal prisoners go now?

The Federal Bureau of Prisons operates three high-security penitentiaries in California and six medium-security federal correctional institutions. In 2024, the government closed the scandal-plagued women’s prison, FCI Dublin, where several guards were found to have sexually abused multiple inmates.