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."
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.