Sister Megan Rice, a Roman Catholic nun who was arrested more than 40 times for protesting America’s military industrial complex, most spectacularly for breaking into one of the world’s largest uranium storage sites, died on Oct. 10 at the residence of her religious order in Rosemont, Pa. She was 91.

Her order, the Society of the Holy Child Jesus, said in a statement that the cause was congestive heart failure.

Sister Rice was a leading figure among antiwar activists, especially the cohort of nuns and priests who saw protesting nuclear weapons as part of their religious calling.

She was already 82 when, in 2012, she and two other antinuclear activists, Greg Boertje-Obed and Michael Walli, hiked through the night over a steep ridge to the outskirts of the Y-12 National Security Complex in Oak Ridge, Tenn.

They used bolt cutters to get through three rings of barbed wire and approached the complex’s newest storage building, a windowless white-concrete hulk that had been billed as the “Fort Knox of uranium.”

They splashed blood against the walls and spray-painted slogans like, “The fruit of justice is peace” and “Woe to an empire of blood.” They lit candles and read an “indictment” against the American nuclear arsenal.

They were surprised at how lax the security was. Several of the cameras that should have captured their approach were broken or turned off, and it took almost half an hour before a single guard approached them. When he did, they broke a loaf of bread and offered him a piece. He refused.

The three activists were arrested and charged with trespassing and “destruction and depredation” of government property. When they refused to plead guilty, prosecutors added a charge of sabotage, carrying up to 20 years in prison.

“Please have no leniency on me,” Sister Rice said during the trial. “To remain in prison for the rest of my life would be the greatest honor you could give me.”

They served just two years and were released after an appeals court vacated the sabotage convictions — though Sister Rice said she would have gladly stayed in prison longer.

“It would be an honor,” she told a reporter for The New York Times soon after her release in 2015. “Good Lord, what would be better than to die in prison for the antinuclear cause?”

The episode at the nuclear complex was just one of many efforts by Sister Rice to take on the American military, a career that led to some 40 arrests — even she lost count — going back to the 1980s. And it was the capstone to a life steeped in progressive Catholicism.

Megan Gillespie Rice, who pronounced her first name MEE-gan, was born on Jan. 31, 1930, in the Morningside Heights section of Manhattan, to a family deeply involved in the Catholic progressive movement. Her father, Frederick Rice, was an obstetrician-gynecologist, and her mother, Madeleine Newman Hooke Rice, was a homemaker who later received a doctorate in history from Columbia.

Both of her parents were active in the Catholic worker movement and were close friends with its founder, Dorothy Day, who Sister Rice remembered visiting her family’s home in Morningside Heights.

Morningside Heights, home to Columbia University and venerable religious institutions like Riverside Church and Union Theological Seminary, was fertile ground for Sister Rice’s religious awakening. Father George Barry Ford, a leader in New York’s civil rights movement, preached at Corpus Christi Church on Columbia’s campus, where her family worshiped, and ran her elementary school.

During World War II, Sister Rice heard rumors about another side of her community: the professors from Columbia who were working on a top-secret government project. Its nature was revealed on Aug. 6, 1945, when the Americans dropped an atomic bomb on Hiroshima, Japan, and dropped another on Nagasaki three days later.

She recalled her mother thanking God for the attack; it meant that her uncle, who was to be part of the invasion of Japan, would now be spared. He went anyway, in the first wave of soldiers to reach Hiroshima after Japan surrendered, and he told her about the horrors he had encountered.

Megan joined the Society of the Holy Child Jesus in 1947 and took her final vows in 1955. She studied biology at Villanova University, and received a master’s degree in cellular biology from Boston College. She then moved to Africa, where she taught in elementary and secondary schools in Nigeria and Ghana.

She leaves no immediate survivors.

Starting in the 1980s, she made frequent trips to the United States, often to participate in antiwar actions.

Sister Rice left Africa for good in 2003. Two years later she moved to Nevada, where she joined an antiwar organization called the Nevada Desert Experience. She was arrested in 2009 during a protest against a missile test at Vandenberg Air Force Base (now Vandenberg Space Force Base) in California, and in 2011 for trespassing on Creech Air Force Base in Nevada, home to the country’s drone warfare program.

She traveled to Tacoma, Wash., in 2011 to observe the trial of several antiwar activists, including Sister Anne Montgomery, an 84-year-old nun, for trespassing on a nuclear submarine base. The trial inspired Sister Rice to plan a similar action of her own.

The protest at Y-12, a year later, made Sister Rice an international celebrity, and she used the spotlight to bring renewed attention to America’s efforts to modernize its nuclear arsenal.

“Sister Megan’s only regret about Y-12 was that she didn’t do something like that earlier,” said Carole Sargent, the author of the forthcoming book “Transform Now Plowshares: Megan Rice, Gregory Boertje-Obed, and Michael Walli.”

The complex shut down for two weeks, and Sister Rice’s incursion spawned Congressional hearings, where representatives thanked her for calling attention to the site’s poor security.

“That young lady there brought a Holy Bible,” said Representative Joe Barton, Republican of Texas. “If she had been a terrorist, the Lord only knows what would have happened.”

It was not the response Sister Rice was hoping for, but it didn’t stop her. After her release, she continued her antiwar activism, joining regular demonstrations outside the White House and the Pentagon.

Spending on nuclear weapons,she said in a 2019 interview is “one of the root causes of, say, poverty in the United States, and therefore of crime.

“It’s a root cause of many other issues because so much money is going into them.”