Eunice Kennedy Shriver, the sister of former President John F. Kennedy and Sen. Ted Kennedy, who helped launch the Special Olympics, died at a Cape Cod hospital at 2 a.m., her family said. She was 88.
Shriver is survived by two siblings, her husband, Robert Sargent Shriver Jr., five children, including NBC reporter and California first lady Maria Shriver, and 19 grandchildren.
"She was the light of our lives, a mother, wife, grandmother, sister and aunt who taught us by example and with passion what it means to live a faith-driven life of love and service to others," the Shriver family said in a written statement. "For each of us, she often seemed to stop time itself -- to run another Special Olympics games, to visit us in our homes, to attend to her own mother, her sisters and brothers, and to sail, tell stories, and laugh and serve her friends."
"Her work transformed the lives of hundreds of millions of people across the globe, and they in turn are her living legacy," the statement said.
While she campaigned for her brother John's presidential campaign and was a frequent face in political and social circles around the country, Shriver is best known for her involvement with the Special Olympics and for helping establish the games 40 years ago.
"Above all, she will be remembered as the founder of the Special Olympics, as a champion for people with intellectual disabilities, and as an extraordinary woman who, as much as anyone, taught our nation -- and our world -- that no physical or mental barrier can restrain the power of the human spirit," President Obama said in a statement. "Her leadership greatly enriched the lives of Special Olympians throughout the world, who have experienced the pride and joy of competition and achievement thanks to her vision."
Born July 10, 1921, Shriver was the fifth of nine children of Joseph Kennedy and Rose Fitzgerald Kennedy.
Family members said she was inspired by her older sister, Rosemary Kennedy, who was mentally handicapped.
"Throughout her extraordinary life, she touched the lives of millions, and for Eunice that was never enough. The seeds of compassion and hope she planted decades ago in her backyard summer camp were inspired by her love for our sister Rosemary," Shriver's brother, Sen. Kennedy, D-Mass., said in a written statement.
"Over the years, she grew those seeds into a worldwide movement that has given persons with disabilities everywhere the opportunity to lead more productive and fulfilling lives. We would never have had an Americans with Disabilities Act without her," Kennedy said.
In a February "Good Morning America" special spotlighting Shriver, Kennedy said his sister was tireless in her efforts.
"Eunice would spend the extra time with Rosemary, teaching her and making sure that she felt included," he said. "It was really that spirit that started the Special Olympics. Eunice is tireless and fearless and reflects a sense of goodness, so it's very difficult for people to say no to Eunice."
It was Shriver's goal to attain equality for the mentally challenged, and she believed they could excel despite their handicaps.
"I love to be with my special friends, and I like to learn from them and their persistence, and their guts, and their courage," Shriver said of her work with athletes with disabilities. "This is the future."
Shriver's friends say she took personal tragedy and transformed it into a movement that changed the lives of millions of people.
"I think the impact was enormous," her friend, Bob Shrum, said on "GMA." "She was a living prayer but she was also witty and warm... and very much her own person."
Eunice Kennedy Shriver's Special Olympics Efforts
Shriver's work started in June 1962 with a day camp in Rockville, Md., for the handicapped, where she taught attendees athletics, floor hockey and aquatics.
In her book about Special Olympics, "Hearts of Gold," author Sheila Dinn writes: "In the summer of 1962, 100 young people with mental retardation came to Mrs. Shriver's camp to run, swim, play soccer, and ride horses. They enjoyed the camp and loved the sports they learned, and by the end of the summer they were 'faster and stronger' than ever before. The doctors and experts had been wrong!"
It was from that camp that the concept of Special Olympics emerged.
Shriver, a former social worker in West Virginia, went on to work as a consultant in President Kennedy's Panel on Mental Retardation.
In December 1968, she helped establish the Special Olympics as a non-profit charitable organization.
In 1984, two years after establishing a National Center for Community of Caring in her name at the University of Utah, Shriver was awarded the Presidential Medal of Freedom by President Ronald Reagan for her work.
"Eunice Kennedy Shriver is a pioneer who literally changed the way persons with intellectual disabilities are treated ... not only in the United States but in Africa and around the world," former South African President Nelson Mandela said of the woman who championed the rights of the mentally disabled.
In 2000, Shriver suffered a health scare after getting an infection following a five-hour surgery to remove a benign pancreatic tumor. But she survived and continued her work on the Special Olympics.
Her husband, a former ambassador to France, was diagnosed with Alzheimer's disease six years ago.
Shriver also inspired her children to do help people with mental disabilities. Shriver's son Tim serves as chairman of the Special Olympics.
"My mother has been a key leader in the field of intellectual disabilities," Maria Shriver has said. "I think she has done more than any single human being alive."
Shriver is the only American woman to have her portrait appear on the commemorative Special Olympics silver dollar during her lifetime.