In 1962, Shriver told the world about Rosemary's condition in a Saturday Evening Post article. The headline read: "Hope for Retarded Children."

Advocates for the mentally disabled point to the article and Shriver's candor as a turning point that helped move mental disabilities from behind a curtain of ignorance.

The article pointed out that Rosemary was raised at home -- in an era when this was scorned -- and avoided mentioning the lobotomy that her father, Joseph P. Kennedy Sr., authorized in 1941 that was meant to help the mildly retarded Rosemary but worsened her condition. She lived most of her life in a private institution in Wisconsin, where Shriver was a frequent visitor, and died at 86 in 2005.

"I had enormous affection for Rosie," Shriver told National Public Radio in 2007. "If I [had] never met Rosemary, never known anything about handicapped children, how would I have ever found out? Because nobody accepted them anyplace."

Influenced by Rosemary's ability at sports and her own inclination toward athletics, Shriver was drawn to the idea of physical activity as a way to benefit the mentally disabled.

"The world was full of people saying what mentally retarded people could not do," her husband of 56 years, former Peace Corps Director Sargent Shriver, recalled some years ago. "She just didn't believe that there were human beings who were as useless or hopeless, or whatever the right word might be, as the mentally retarded were thought to be 40 years ago."

In 1961, Eunice Shriver turned Timberlawn, the family farm in Maryland, into a free day camp for mentally disabled children. She would get down in the dirt with campers, play in the sandbox, pitch softballs or teach them to swim. Shriver had them riding horseback and shooting bows and arrows.

"Nobody else's mother was doing anything like that," Maria Shriver said in the 1994 book "The Kennedy Women," by Laurence Leamer. "It was always my mother following her own gut going against the grain."

When an idea was floated to stage a summer athletic festival for the mentally disabled, Eunice Shriver suggested broadening the concept to include participants from around the country. She had the Joseph P. Kennedy Jr. Foundation -- named for her oldest sibling, who was killed in World War II -- pay for them.

The first games were held in Chicago in the summer of 1968, just weeks after the assassination of Robert Kennedy. In her opening address to about 1,000 competitors from 26 states and Canada, Shriver noted that the event was neither a spectacle "nor just for fun." She wanted to prove that, through sports, these "exceptional children" could reach their potential.

Midway through the inaugural competition, which featured only swimming and track and field events, Chicago Mayor Richard J. Daley told Shriver: "Eunice, the world will never be the same after these games."

He was right. Today the Special Olympics are played on a worldwide stage, with an estimated 2.5 million people from more than 150 countries taking part in hundreds of programs. Athletes as young as 8 attend winter and summer games that have been staged every four years since the 1970s.

At the 2007 summer games in Shanghai, more than 7,200 athletes competed in 21 events that now include such sports as gymnastics, cycling and golf.

Shriver told NPR in 2007 that she continued to work for the mentally disabled "because it's so outrageous, still. In so many countries. They're not accepted . . . . So we have much to do."

Eunice Mary Kennedy -- known within the family as "Puny Eunie" -- was born July 10, 1921, at home in Brookline, Mass. The fifth of nine children of Joseph P. and Rose Fitzgerald Kennedy had chronic health problems all her life: Addison's disease, an adrenal disorder that also plagued her brother John; stomach ulcers; colitis; and a tendency toward nervous exhaustion.

Yet Shriver's fervent drive easily exhausted aides half her age and others around her.

She had "all that incredible energy," Maria Shriver recalled in "The Kennedy Women." "People think, 'God, it would be such a horror if your mother had really great health. What would she have been like?' "

Eunice Kennedy attended Stanford University because her mother thought the mild California climate might improve her health.

After graduating in 1944 with a bachelor's degree in sociology, she worked for the State Department reorienting American prisoners of war after World War II. She also was a social worker at the Penitentiary for Women in Alderson, W.Va., and later worked for the Justice Department as coordinator of the National Conference on Prevention and Control of Juvenile Delinquency.

At a cocktail party in New York City in 1946, she met Robert Sargent Shriver Jr., a Navy veteran and Yale Law School graduate who worked on her father's business staff. They married in 1953 in front of 1,700 guests at St. Patrick's Cathedral in New York City, bolstering what has been described as both an American and a Catholic aristocracy.