In 1958, her father asked Sargent and Eunice to run the foundation named for Joseph Jr. The senior Kennedy, reportedly tormented by the fate of his daughter Rosemary, was also looking for a cause to which the family name could be linked.

When JFK was elected president two years later, and Sargent Shriver was asked to run the Peace Corps, the foundation's leadership fell squarely to Eunice.

In her hands, the cause of mental retardation "became an incandescent torch," Shorter wrote in his book.

She couldn't have accomplished more during JFK's presidency if she had been given an official role, Eunice Shriver told Leamer in "The Kennedy Women" decades later.

"I was perfectly happy where I was," she said. "And I think I just had a very wonderful relationship with my brother, and he was wonderful to this cause. I don't say that blindly."

Few avenues existed for the study of intellectual disabilities when the Kennedy foundation was established in 1946. One of the first centers the organization founded to diagnose and treat such disabilities is now known as the St. John's Child and Family Development Center in Santa Monica.

The foundation created a network of mental retardation research centers at medical schools at major universities, including Johns Hopkins, Harvard and Stanford. It also established centers for the study of medical ethics at Harvard and Georgetown universities.

Eunice and Sargent Shriver's marriage was widely considered the best in the big Kennedy clan. Both were regular churchgoers committed to public service, and they made room for fun. When Sargent Shriver was U.S. ambassador to France from 1968 to 1970, his wife installed a trampoline on the residence lawn and often invited diplomats to bounce a bit.

In 1984, Eunice Shriver received the Presidential Medal of Freedom, the nation's highest civilian honor. Her many accolades included the French Legion of Honor, the Lasker Award for public service and the Theodore Roosevelt Award of the National Collegiate Athletic Assn.

The next generation of the Kennedys often cited Eunice as the family member they looked up to most.

"She should have been president," her nephew Bobby Kennedy said in the 1983 book "Growing Up Kennedy." "She is the most impressive figure in the family. Most of my brothers, sisters and cousins would say they'd like to be like her."

Yet Shriver, the mother of four sons and a daughter, thoroughly believed "in motherhood as the nourishment of life," once writing that "it is the most wonderful, satisfying thing we can do."

Son Mark was a member of the Maryland Legislature. Timothy has chaired the Special Olympics for more than a dozen years. Bobby is a Santa Monica city councilman and film producer. Anthony heads Best Buddies, which pairs college students with the mentally challenged. Maria, a former network news reporter, is also active in the Special Olympics.

Besides her children, Shriver is survived by her husband, 93, who has Alzheimer's disease; brother Edward, who was diagnosed with a malignant brain tumor in 2008; sister Jean Kennedy Smith;and 19 grandchildren.