WASHINGTON (CNN) -- Commemorating the long fight toward racial equality that many say hasn't ended, marchers on the National Mall on Wednesday -- including President Barack Obama -- commemorated the 50th anniversary of the Rev. Martin Luther King Jr.'s "I Have a Dream" speech.
On that August day in 1963, when King and his fellow marchers attended what he labeled "the greatest demonstration for freedom in the history of our nation," few in that crowd could have imagined that half a century later, an African-American president of the United States would mark the occasion with a speech in the same location.
"His words belong to the ages, possessing a power and prophecy unmatched in our time," Obama told a crowd that gathered under gray skies and intermittent drizzle to attend the five-hour ceremony.
King, Obama said, "gave mighty voice to the quiet hopes of millions," heralding leaders who braved intimidation and violence in their fight for equal rights.
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"Because they kept marching, America changed. Because they marched, the civil rights law was passed. Because they marched, a voting rights law was signed," Obama said. "Because they marched, city councils changed and state legislatures changed and Congress changed and, yes, eventually, the White House changed."
While speakers Wednesday marked the great progress toward King's goal of racial accord, many suggested that the dream was far from realized, citing high minority unemployment, voter identification laws that critics say prevent African-Americans from casting ballots, and the verdict in the closely watched Trayvon Martin murder trial.
"We have come a great distance in this country in the 50 years. But we still have a great distance to go before we fulfill the dream of Martin Luther King Jr.," said U.S. Rep. John Lewis, D-Georgia, adding that progress toward King's goal could be marked by his own election to Congress.
"But there are still invisible signs, barriers in the hearts of humankind that form a gulf between us," Lewis said.
Another leader from King's era of the civil rights movement, Myrlie Evers-Williams, said the United States had "certainly taken a turn backwards" in the quest for civil rights.
Former President Jimmy Carter, speaking ahead of Obama, asserted that recent developments in American policy would have disappointed King.
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"I believe we all know how Dr. King would have reacted to the new ID requirements to exclude certain voters, especially African-Americans," said Carter, a Democrat. "I think we all know how Dr. King would have reacted to the Supreme Court striking down a crucial part of the Voting Rights Act just recently passed overwhelmingly by Congress."
Another Democratic president, Bill Clinton, argued during his speech for working together against stalemates and inaction, saying King "did not live and die to hear his heirs whine about political gridlock."
"It is time to stop complaining and put our shoulders against the stubborn gates holding the American people back," Clinton said.
Neither of the living former Republican presidents attended Wednesday's event. George H.W. Bush and his son George W. Bush both opted out, citing health concerns. The latter is recovering from a recent heart procedure.
Before Obama addressed the throngs gathered at the Lincoln Memorial, civil rights leaders past and present remembered the decades-long movement to secure equal treatment and rights for African-Americans.
Celebrities and entertainers at the event included Forest Whitaker and Oprah Winfrey, who star as husband and wife in one of the summer's hottest movies, "Lee Daniels' The Butler," about life in the White House through the eyes of the (mostly black) hired help.
Winfrey declared King had seen injustice and "refused to look the other way."
"We, too, can be courageous by continuing to walk in the footsteps of the path that he forged," Winfrey said.
Two musicians who performed at the 1963 march also sang Wednesday. Peter Yarrow and Paul Stookey, from the trio Peter, Paul and Mary, sang Bob Dylan's "Blowin' in the Wind," backed by Sybrina Fulton and Tracy Martin, the parents of Trayvon Martin, whose 2012 shooting death sparked a national conversation about race. Mary Travers, the third artist in the group, died in 2009.
Obama's most personal remarks on race to date came in the aftermath of the July verdict that found Martin's killer not guilty.
A White House official said the president had spoken to several people about his speech, including Lewis.
The Rev. Jesse L. Jackson, a contemporary of King's who was with him the night he died, sees Obama as the finest product of the modern civil rights movement that began in the mid-1950s.
Obama "is the crown jewel of that movement," Jackson said.
But Jackson also said he sees Obama in a completely different group
of leaders from King.
"He is in the category of Lincoln, Roosevelt, Johnson. Dr. King is in the category of Frederick Douglass. Clarence Thomas would be in the category of Thurgood Marshall. We should not confuse his roles to that extent," he said.
The present moment has done more than prompt comparisons between King and Obama.
It has also spurred debate over the "dream" about which King spoke so eloquently. Jackson said there was more than one dream for King and the civil rights movement before his assassination in 1968.
"The dream in '63 was to overcome humiliation. ... The dream of '64 was public accommodations, to make that legal. The dream of '65 was the right to vote. The dream of '66 was fair and open housing. The dream of '67 was a Poor People's campaign and to choose the war on poverty over the war in Vietnam. And he was a very different person in '68 because he was under such attacks ... and he was finally killed."
But to many, the "dream" that King articulated is -- more than anything else -- about racial equality and justice. And the question is how close to the goal we've gotten in a country that just re-elected its first black president.
Social activist Robert Woodson, who heads the Center for Neighborhood Enterprise, said the African-American community faced a completely different set of issues in the 1960s. "Our problems today are not the Klan coming in, but it is, what are we doing to ourselves?"
Woodson added, "About 10 years ago, there was a Klan rally in downtown Washington, and The Washington Post asked an old black guy in (mostly black) Ward 8 -- the highest crime area of the city -- if he was going to join in the demonstration. He said, 'Bring the Klan down here if they can get rid of these drug dealers.' "
Woodson, who is black and describes himself an independent, is highly critical of the current state of civil rights advocacy. He recently addressed a meeting of the Republican National Committee, echoing some of his concerns about the movement and the state of black leadership.
"I really think it has morphed into a race-grievance industry. I think they have descended from the moral high ground that they used to occupy. And that they have become an extension of the Democratic Party," Woodson said.
Some conservatives have criticized the 50th anniversary celebration as an exercise of liberal Democratic politics, though the organizers have said the agenda is nonpartisan.
Organized labor; lesbian, gay, bisexual and transgender groups; and opponents of "stand your ground" laws all see Wednesday's event as an opportunity to get their messages out.
However, many Republicans have chosen to remain on the sidelines.
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