Oprah, Jamie Foxx Stump for Civil Rights at March on Washington Rally

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Forest Whitaker also joined President Barack Obama at the Lincoln Memorial event honoring the 50th anniversary of Martin Luther King Jr.'s "I Have a Dream" speech.

On the 50th anniversary Wednesday of the March on Washington, Oprah Winfrey, Jamie Foxx and Forest Whitaker led a celebrity contingent in joining President Barack Obama at the Lincoln Memorial in honoring the memory of Dr. Martin Luther King and his classic "I Have a Dream" speech.

The stars tried in their own way -- as the president did -- to express what the Civil Rights Movement and King's part in it continues to mean to them.

"On this date, in this place, at this time, 50 years ago today, Dr. Martin Luther King shared his dream for America with America," Winfrey told the crowd, estimated at "tens of thousands." "Took me 50 years, but I’m here."

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She called King a "passionate voice that awakened the conscience of a nation."

"Dr. King believed that our destinies are all intertwined, and he knew that our hopes and our dreams are really all the same," Winfrey said. "He challenged us to see how we all are more alike than we are different."

For his part, Foxx called on his fellow black entertainers to renew their commitment to civil rights and to demonstrate the sort of intensity that earlier generations of entertainers, such as Harry Belafonte, 86, showed throughout their careers. Foxx recalled a meeting with Belafonte and a subsequent dinner in which the singer challenged him to do just that.

Whitaker drew on his experience as an UNESCO Goodwill Ambassador for Peace to talk about the continued relevance of King's insight in a world still racked by turmoil, violence and poverty.

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"In my travels as a goodwill ambassador both here and abroad I've observed revolutions and social change first hand," Whitaker said. "I've seen youths senselessly killed, people struggling for food, a decent home, education and justice. I'm often reminded of the marches and the sit-ins we experienced here during the '60s. And I remember the words of Dr. Martin Luther King, which were 'I have decided to stick with love. Hate is too great a burden to bear.'"

Other celebrities appearing at the event Wednesday included Hill Harper,  TV journalist Soledad O’Brien, LeAnn Rimes and the Winans brothers.  The tween singing trio Identity4Pop, managed by Alex Avant, sang the National Anthem.

O'Brien, whose next installment of her documentary series "Black in America" will air on CNN on Friday night, said she was honored when the King family asked her recently to participate in the event. She traveled from New York to Washington with her 9-year-old twin sons and teenage daughter.

"Imagine being able to say all those many years ago, 'I was there,'" O'Brien told THR. "Now I can say I was at the 50th anniversary. It's really an incredible thing.

"The March on Washington is something I've covered in various ways for a long time," said the former CNN anchor, who is independently producing documentaries for various outlets as part of her Starfish Media Group. "It's about Dr. King's speech and much more. It's about the individual people who came all this way and turned the march into a moment that would change history. "