The cause of death was congestive heart failure, Reagan's assistant Allison Borio told the Associated Press.
"Mrs. Reagan will be buried at the Ronald Reagan Presidential Library in Simi Valley, California, next to her husband, Ronald Wilson Reagan, who died on June 5, 2004," said a statement released by the Reagan Foundation. "Prior to the funeral service, there will be an opportunity for members of the public to pay their respects at the Library. Details will be announced shortly. In lieu of flowers, Mrs. Reagan requested that contributions be made to the Ronald Reagan Presidential Library and Foundation at www.reaganlibrary.com.
People coming to the library in Simi Valley on Sunday left a growing display of flowers at the main entrance gate. The library was closed and visitors were being turned away.
Sharon Hirtzer and her husband, Joe, were among the mourners outside the library. The Chicago couple were in California and had previously planned to visit the library before learning of Mrs. Reagan's death.
"I was just really said," Sharon Hirtzer said. "She was a great lady and had so much class."
Also outside the library grounds was veteran Andy Hall, who waved a large U.S. flag and said he served in the Army during the Reagan presidency. "Seems appropriate to come out and just take some time to show my respect," Hall said.
Like most first ladies, Nancy Reagan was the target of both praise and criticism. She brought an elegance to the White House that some thought was long overdue. But others said it was the sign of an out-of-touch administration during tough economic times. Reagan was criticized for meddling in White House affairs, but she was also credited with her "Just Say No" campaign against drug abuse.
Later in life, Reagan nursed the former president during his long struggle with Alzheimer's disease. She later became a strong advocate for stem-cell research, in the hope that it would lead to a cure.
Reagan's major role in life was to be the supportive, adoring wife of the nation's 40th president. Admirers and detractors alike marveled at their close relationship and how it sustained them during the sometimes grueling journey of public life. She was President Reagan's fiercest protector — and eventually his caregiver, as he was ravaged by Alzheimer's.
Despite the criticism Reagan received during her time in the White House, her husband's difficult, final days brought her widespread sympathy. At the 1996 Republican convention, she had many, including herself, in tears.
"Just four years ago, Ronnie stood before you and spoke for what he said might be his last speech at a Republican convention. Sadly his words were too prophetic," she said.
Over the next eight years, Reagan watched as her once powerful husband deteriorated, both physically and mentally. It was a long, sad goodbye for a woman who said her life truly began when she married Ronald Reagan.
Nancy Reagan was born in 1921 as Anne Frances Robbins. She became an actress, like her mother. But as she later told C-SPAN, it was hardly a passion.
"I had gone to college and graduated and hadn't found the man I wanted to marry. I didn't want to sit in Chicago and do nothing, so I became an actress," she said.
Her big break came in 1949, when, as Nancy Davis, she landed a seven-year contract with MGM. She went on to make a number of moderately successful films. But as Ronald Reagan's biographer Edmund Morris says, her real career began when she met the handsome president of the Screen Actors Guild.
"Nancy loved Ronald Reagan with a consuming passion. He was her one and only reason for existence," Morris says.
The two married in 1952. In 1966, Ronald Reagan was elected governor of California. As the state's first lady, Nancy Reagan got her first taste of political sniping, most often for the doe-eyed, adoring look she always gave her husband — something known as The Gaze.
But that was nothing compared with the criticism she faced when she came to Washington and decided to redecorate the White House and buy expensive new china. First lady historian Carl Sferrazza Anthony says it wasn't the best move, with the new administration cutting billions from the federal budget.
"Doing this at a time of recession and high unemployment made her an unwitting symbol for the Democrats of everything that was wrong about so-called Reaganomics," Anthony says. "And she was very hurt by this."
Anthony says it would take Reagan years to learn how much impact her actions as first lady could have. But those initial controversies were soon overshadowed.
The attempted assassination of President Reagan in March 1981 devastated the first lady, who saw all too clearly how quickly her husband could be taken away.
"He came very close to dying. I don't think most people knew that then. I don't think most people know it now," she said. "But there were two times that they came to me and said they couldn't find his pulse."
She told NPR's Terry Gross in 1989 that it was then she decided to consult an astrologer.
"When a friend called me and said I know this lady who said that if she only could have gotten to you she could have told you that he shouldn't have done anything that day," she said, "and I thought, 'Oh my lord, I could have saved him maybe.' "
'Just Say No'
Reagan began to rely on the astrologer to help set the president's agenda, something the public wouldn't know for years. She also began to take on the more traditional first lady role of promoting a pet project — in her case, the "Just Say No" anti-drug campaign. She spoke on the issue around the country and in 1986, joined the president for a televised address to the nation.
"We want you to help us create an outspoken intolerance for drug use. For the sake of our children, I implore each of you to be unyielding and inflexible in your opposition to drugs," she said.
But that didn't stop the criticism. In Reagan's second term, the first lady was increasingly accused of interfering in White House affairs. When one reporter asked the president about U.S.-Soviet space weapons talks, she was overheard whispering, "We're doing everything we can," something President Reagan promptly repeated. But Anthony says Nancy Reagan had only one goal in mind — protecting her husband and his image.
"Mrs. Reagan I think had enormous political influence without always intending to," Anthony says.
He says she was constantly on the lookout for anyone she thought didn't have her husband's best interests at heart — most notably, White House Chief of Staff Don Regan, whose ouster she helped to orchestrate. It was telling that Regan's replacement, former Sen. Howard Baker, was grilled by reporters his first day on the job about his relationship with the first lady.
Morris says Nancy Reagan's political instincts were invaluable for a president inclined to trust and like everyone around him.
"He needed a screen, a protector. That's the only real political function she formed for him. She could see a predator coming from a mile off," he says.
Republican Party's Matriarch
Anthony adds that Nancy Reagan was more independent and outspoken than many gave her credit for. He notes, for example, that the first lady supported abortion rights in an anti-abortion administration. He thinks she also grew with the job.
"You see a woman who, despite having been an actress, was at first slightly uncomfortable even giving the teacher of the year award. Then eight years later [she] is addressing the United Nations General Assembly," Anthony says.
In fact, she was the first first lady to do so. And she continued to have an impact long after leaving the White House. She became a strong advocate of stem-cell research — in the hope that it would lead to an Alzheimer's cure — even though it put her at odds with many Republicans.
Still, she was clearly the party's matriarch — a reminder of a popular president and the woman who protected him.
At a June 2009 ceremony to unveil a statue of her husband in the Capitol rotunda, Reagan was greeted with extended applause from lawmakers of both parties. Her voice cracked as she noted that the last time she'd been in the room had been for her husband's state funeral. She then thanked everyone for all their support and left the stage.
Reactions across the world
Reactions to the Nancy Reagan's passing and reflections on her accomplishments poured in Sunday on social media and as press releases:
President Obama and first lady Michelle Obama:
Nancy Reagan once wrote that nothing could prepare you for living in the White House. She was right, of course. But we had a head start, because we were fortunate to benefit from her proud example, and her warm and generous advice.
Our former First Lady redefined the role in her time here. Later, in her long goodbye with President Reagan, she became a voice on behalf of millions of families going through the depleting, aching reality of Alzheimer’s, and took on a new role, as advocate, on behalf of treatments that hold the potential and the promise to improve and save lives.
We offer our sincere condolences to their children, Patti, Ron, and Michael, and to their grandchildren. And we remain grateful for Nancy Reagan's life, thankful for her guidance, and prayerful that she and her beloved husband are together again.
Former Republican presidential candidate and Massachusetts governor Mitt Romney:
"With the passing of Nancy Reagan, we say a final goodbye to the days of Ronald Reagan. With charm, grace, and a passion for America, this couple reminded us of the greatness and the endurance of the American experiment. Some underestimate the influence of a First Lady but from Martha and Abigail through Nancy and beyond, these women have shaped policy, strengthened resolve, and drawn on our better angels. God and Ronnie have finally welcomed a choice soul home."
Actor and former California governor Arnold Schwarzenegger:
"Nancy Reagan was one of my heroes. She served as first lady with unbelievable power, class and grace and left her mark on the world. She's with her Ronnie now, but those of us she left behind will miss her dearly."
Former first lady Barbara Bush:
"Nancy Reagan was totally devoted to President Reagan, and we take comfort that they will be reunited once more. George and I send our prayers and condolences to her family."
Republican presidential candidate and Senator Ted Cruz:
"Nancy Reagan will be remembered for her deep passion for this nation and love for her husband, Ronald. The Reagan family is in our prayers."
Republican presidential candidate and businessman Donald Trump:
"Nancy Reagan, the wife of a truly great President, was an amazing woman. She will be missed!"
Former President George W. Bush:
"Laura and I are saddened by the loss of former first lady Nancy Reagan. Mrs. Reagan was fiercely loyal to her beloved husband, and that devotion was matched only by her devotion to our country. Her influence on the White House was complete and lasting. During her time as first lady and since, she raised awareness about drug abuse and breast cancer. When we moved into the White House, we benefited from her work to make those historic rooms beautiful. Laura and I are grateful for the life of Nancy Reagan, and we send our condolences to the entire Reagan family."
Republican National Committee Chairman Reince Priebus:
"Nancy Reagan embodied what it means to represent America as first lady and her dignified and warm demeanor inspired America. Mrs. Reagan will go down in history as a woman who left her own mark on the White House and our country. She was a longtime friend and supporter of many in our party, and will be sorely missed."
Former President Jimmy Carter:
"President Reagan has been reunited with his wife and partner but America and the Reagan family have lost a woman of grace and strength. I join people from around the country and the world in sending them our best thoughts and prayers during this difficult time. A woman of strength and wit, Nancy Reagan's dedication to our country was matched only by that of her husband. Theirs was one of our nation's great love stories and a model of shared devotion to our country. America is stronger and better for their service."
Democratic National Committee Chairwoman, Rep. Debbie Wasserman Schultz:
"Mrs. Reagan understood the enormous responsibility that comes with representing our nation from the White House on the world stage, and she was beloved by the American people for her grace and dignity in that role. Her 'Just Say No' campaign to keep children from abusing drugs had a long-lasting impact that no doubt saved lives. And her work later in life to support the National Alzheimer's Association and stem cell research helped advance the science of finding a cure for a devastating disease that affects millions of American families every day."
California Gov. Jerry Brown:
“Nancy Reagan lived a remarkable life and will be remembered for her strength and grace. On behalf of all Californians, Anne and I extend our deepest condolences to the Reagan family.”
Former President Bill Clinton and Democratic presidential candidate Hillary Clinton:
"Nancy was an extraordinary woman: a gracious first lady, proud mother and devoted wife to President Reagan — her Ronnie. Her strength of character was legendary, particularly when tested by the attempted assassination of the president, and throughout his battle with Alzheimer's. She leaves a remarkable legacy of good."
Republican presidential candidate and senator Marco Rubio:
"Today our nation mourns the loss of Nancy Reagan, a true example of integrity and grace. My prayers are with the entire Reagan family."
Israel Prime Minister Benjamin Netanyahu:
"I remember Nancy as a noble woman who supported President Reagan and stood by his side. She will be remembered as a great friend of the State of Israel."
California Senator Barbara Boxer:
"My deepest condolences go to the Reagan family on the passing of Nancy Reagan. She set an example as a First Lady who truly stood on her own as a force. She made a lasting contribution to the fight against Alzheimer's and her support of the Brady bill made the difference."
Democratic presidential candidate and senator Bernie Sanders:
"Nancy Reagan was an exemplary first lady. Even after her time in the White House, she was an outspoken advocate for stem-cell research to find a cure for Alzheimer's. Nancy Reagan had a good heart, and she will be dearly missed."
Former Republican presidential candidate and senator John McCain:
"Nancy Reagan was an example to us all of graciousness, loyalty and dignity in good times and bad. She was an exemplary first lady. I will always remember her as a dear friend and patriot and as one-half of a love story that Hollywood couldn't have written any better."
California Republican Rep. Darrell Issa:
"To meet Nancy Reagan was to witness her quiet dignity and personal resolve. To know her was to marvel at her tireless dedication and boundless love for her husband. There was no bigger champion of the man, nor any fiercer protector of his memory than Nancy Reagan. They say great men are nothing more than the ones who helped them get there. With Nancy, there's no question that her unyielding devotion helped her husband achieve all that he did. I am honored to have had her friendship and she will truly be missed.''
Los Angeles County Supervisor Mike Antonovich:
"Nancy Reagan was a friend and role model who served her country as first lady with grace and dignity. She was a vital partner when Ronald Reagan was governor and later president. She always supported him without reservation as he led our state and nation. She will be missed."
Reports from the Associated Press were included in this article.