Former U.S. first lady Barbara Bush has died at the age of 92, her family said.
"A former First Lady of the United States of America and relentless proponent of family literacy, Barbara Pierce Bush passed away Tuesday, April 17, 2018, at the age of 92," the office of her now widower, former U.S. President George H.W. Bush, said in a statement.
They were married for 73 years, and Mrs. Bush was one of only two U.S. first ladies who was also the mother of a president.
The couple's son, George W. Bush, served two terms as U.S. president, from 2001 to 2009. Another of their sons, Jeb Bush, is a former Florida governor and onetime Republican presidential candidate.
Mrs. Bush served as first lady from 1989 to 1993, embracing universal literacy as a focus of her time in the White House.
She and her husband, who were married in 1945, had the longest marriage of any U.S. presidential couple in the history of the country.
"I had the best job in America," she wrote of her time in the White House in a 1994 memoir. "Every single day was interesting, rewarding, and sometimes just plain fun."
Her popularity was often greater than that of her husband's, according to opinion polls.
"I don't threaten anyone," she said. "That's because I'm everyone's grandma."
A spokesman for the family had said on April 15 that the former first lady had opted to decline continuing medical treatment for health difficulties in favor of "comfort care" at home in Houston, Texas.
She had recently been hospitalized with heart problems and had reporetedly been previously treated for a thyroid condition.
U.S. President Donald Trump and his wife, Melania, hailed the former first lady as an "advocate of the American family."
"Amongst her greatest achievements was recognizing the importance of literacy as a fundamental family value that requires nurturing and protection," Trump said.
"She will be long remembered for her strong devotion to country and family, both of which she served unfailingly well," they added.
Other tributes poured in from former U.S. presidents and other dignitaries.
Trump's predecessor, Barack Obama, and former first lady Michele Obama praised Mrs. Bush as "the rock of a family dedicated to public service" and called her "an example of the humility and decency that reflects the very best of the American spirit."
Former President Bill Clinton and his wife, former Secretary of State Hillary Clinton, called her a "remarkable woman" with "grit and grace, brains and beauty."
"She was fierce and feisty in support of her family and friends, her country and her causes. She showed us what an honest, vibrant, full life looks like," the Clintons said.
Former President George W. Bush, called his mother "a fabulous First Lady and a woman unlike any other who brought levity, love, and literacy to millions."
"Mom kept us on our toes and kept us laughing until the end. I'm a lucky man that Barbara Bush was my mother," he said.
The daughter of the publisher of McCall's magazine, she was born Barbara Pierce on June 8, 1925, and grew up in Rye, New York.
She met her future husband at a party in Connecticut in 1941.
The couple made one of their final public appearances by attending the 2017 Super Bowl in Houston.