WASHINGTON -- On the steps of the Lincoln Memorial where the Rev. Martin Luther King Jr. 50 years ago sounded a call "to let freedom ring," President Barack Obama Wednesday stood as a symbol of King's dream and urged Americans to keep marching for justice and economic opportunity.
Tens of thousands of people crowded around the reflecting pool to mark the 50th anniversary of the March on Washington for Jobs and Freedom and King's "I Have a Dream" speech and to hear stories and songs of the civil rights movement, reflections on its meaning and renewed calls to action.
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"Because they kept marching, America changed," Obama said, paying homage to the famous and the unknowns who put their lives on the line.
"To dismiss the magnitude of this progress -- to suggest as some sometimes do that little has changed -- that dishonors the courage and sacrifice of those who paid the price to march in those years . . . " he said. "But we would dishonor those heroes as well to suggest that the work of this nation is somehow complete. The arc of the moral universe may bend towards justice, but it doesn't bend on its own.
"They were seeking jobs as well as justice; not just the absence of oppression, but the presence of economic opportunity," Obama said to applause.
"The test was not and never has been whether the doors of opportunity are cracked a bit wider for a few," the president said. "It was whether our economic system provides a fair shot for the many, for the black custodian and the white steelworker, the immigrant dishwasher and the Native American veteran. To win that battle, to answer that call -- this remains our great unfinished business."
The five-hour ceremony was filled with symbolism and references to King's landmark speech and the events of the era.
The rally, like the re-enactment of the march held on Saturday, was broad and inclusive, featuring labor leaders, environmentalists, disability activists, gays and lesbians, Latinos, Asians and even Maori dancers from New Zealand.
But speakers also attacked the Supreme Court's striking down of part of the Voting Rights Act of 1965, the not-guilty verdict in the Trayvon Martin killing in Florida, and the stop-and-frisk law in New York City.
Decrying economic inequality, Obama attacked the "entrenched interests" whose corporate profits are soaring while workers' wages are stagnating.
Unlike the march in 1963 at which no politicians appeared, the commemoration Wednesday included two former presidents, Jimmy Carter and Bill Clinton, and the first black president of the United States.
Carter spoke of the pride he had in coming from the same state as King and his friendship with King's family, yet he said he knew that King would be troubled by states creating new hurdles for voting rights.
Clinton recalled the impact of the televised march on him as "a 17-year-old boy watching alone in his home in Arkansas."
He also told the crowd, "It is time to stop complaining and put our shoulders against the stubborn gates holding the American people back."
Rep. John Lewis (D-Ga.), the only surviving speaker from the 1963 march, retold the story of that day. "This moment in history has been a long time coming, but a change has come," he said.
Also striding across the Lincoln Memorial's steps were Caroline Kennedy, who recalled how her father, President John F. Kennedy, put the force of the government on the side of marchers; and Linda Byrd Johnson Robb, who recalled how her "daddy" said he was proudest of the three civil rights acts he signed into law.
King's family was represented by his son Martin, daughter Bernice and sister Christine King Farris. Celebrities who spoke included Oprah Winfrey and movie stars Jamie Foxx and Forrest Whitaker, basketball star Bill Russell and others.
Before the rally, marchers followed a replica of the bus in which Rosa Parks was riding on Dec. 1, 1955, when she refused to give up her seat to a white man and was arrested, setting off the bus boycott in Montgomery, Ala., that launched the civil rights movement.
At 3 p.m., bells around the country rang at local ceremonies to honor the moment King spoke five decades ago.
At the Lincoln Memorial, organizers rang a bell taken from the Birmingham, Ala., church bombed by the Ku Klux Klan, killing four black girls three weeks after the 1963 march.