Tennis trailblazer Althea Gibson, the first African-American player to win the Wimbledon and U.S. national championships, died Sunday of respiratory failure in an East Orange, N.J., hospital, according to published reports.

Gibson, 76, had been seriously ill for some time but had only been in the hospital for two days before her death, Fran Clayton Gray, her friend and co-founder of the Althea Gibson Foundation, told Reuters.

The daughter of a South Carolina sharecropper and raised in Harlem, Gibson, known as a tall and powerful presence, dominated women's tennis in the late 1950s --- just as the civil-rights movement was growing -- and is a member of the International Tennis Hall of Fame. Venus Williams acknowledged Gibson's contribution to the sport when she won the U.S. Open in 2000.

"The last time I saw her," Gibson's friend Zina Garrison told The Washington Post, "my boyfriend said, 'Even you don't realize what an icon she is. We all take it for granted (that she is) one of our national heroes.' And I knew it was true."

Gibson became the first African-American to play in the U.S. championships in 1950 after winning a string of titles in the all-black American Tennis Association. She broke the racial barrier at Wimbledon in 1951. Five years later, she became the first black woman to win a major tennis crown by taking the French championship title, Reuters reports.

In 1957, Gibson then became the first African-American to win the Wimbledon women's singles title, and she repeated the feat by claiming the U.S. national crown at Forest Hills.

Although Gibson dominated the next season, again sweeping Wimbledon and the U.S. championships, she retired from the amateur ranks after the 1958 season. In all, she won 11 major tennis titles in singles and doubles.

She then turned to golf and in 1964 became the first African-American to join the Ladies Professional Golf Association (LPGA) tour, though she never won at the game and quit the tour in 1971.

Gibson went on to become New Jersey state commissioner of athletics in 1975, a position she held for a decade. She married and divorced twice, to William Darbien and Sidney Llewellyn, both of whom pre-deceased her.