Her death follows a series of strokes over the past several years. At the time of her death, Shriver's husband, five children and all 19 grandchildren were by her side, according to a family statement.
"She set out to change the world and to change us, and she did that and more," the statement read.
Shriver, a sister of President John F. Kennedy and Sens. Robert F. Kennedy and Edward M. Kennedy, as well the mother-in-law to Gov. Arnold Schwarzenegger of California, is widely credited with removing the stigma once associated with mental retardation in the United States. At the outset of her work on behalf of the mentally challenged in the late 1950s, those with intellectual disabilities were often cast aside by society. Thanks to her efforts, the nation and the world now understand "that no physical or mental barrier can restrain the power of the human spirit," President Barack Obama said in a statement.
Watch a 2006 NewsHour profile of Shriver and an interview with her son, Tim Shriver.
Her efforts began in 1957 as vice president of the Joseph P. Kennedy Jr. Foundation, which concentated on improving the ways in which society deals with people with intellectual disabilities. The foundation was instrumental in the formation of President Kennedy's 1961 Panel on Mental Retardation, and the development of the National Institute of Child Health and Human Development.
Most notably, Shriver's work at the Joseph M. Kennedy Jr. Foundation helped establish the First International Special Olympics Summer Games in 1968. The inaugural games, held in Chicago, brought together 1,000 athletes from 26 states and Canada. Today, the competition comprises nearly 3 million athletes in more than 180 countries.
Growing up, Shriver learned firsthand about the difficulties of the mentally challenged through her relationship with her older sister, Rosemary, who was born with mild retardation in 1918. Rosemary spent her childhood in the Kennedy household, unlike many developmentally challenged children at the time who were instead placed in institutions.
"I think really in those early days, playing touch football, just being in a family, a large family, where one child had some special needs, my mother knew from that experience -- not from knowledge, not from reading in a book, but from her heart -- that her sister could do things, and particularly do things in sports," Shriver's son, and chairman of the Special Olympics, Tim Shriver, told the NewsHour in 2006.
Shriver, for her own part, echoed those sentiments in a groundbreaking 1962 article in the Saturday Evening Post. In it, she wrote, "Like diabetes, deafness, polio, or any other misfortune, mental retardation can happen in any family."
"The truth is," she added, "that 75 to 85 percent of the retarded are capable of becoming useful citizens with the help of special education and rehabilitation. Another 10 percent can learn to make small contributions, not involving book learning, such as mowing a lawn or washing dishes."
---- Compiled from wire reports and other media sources