His vision of a land where little black boys and girls in the South would one day hold hands with little white boys and girls was remembered by thousands of people who gathered on a warm summer day to celebrate the coming anniversary of King's "I Have a Dream" speech.
"Despite the progress we've made during the last four decades, people of color are still being denied a fair share of employment and educational opportunities in our society," said his son, Martin Luther King III.
Speaking to a few thousand people gathered on the steps of the Lincoln Memorial, King said it was a day to honor the hard work of all those behind the 1963 march. It also represented, he said, a moment of realization that much work lies ahead.
To mark the anniversary of the March on Washington that culminated in the speech, King's widow, Coretta Scott King, urged the crowd to follow the peaceful path that her husband preached.
"We must make our hearts instruments of peace and nonviolence because when the heart is right, the mind and the body will follow," she said.
Mrs. King stood on the memorial's granite steps, looking out over the Reflecting Pool, in the same spot where her husband delivered his powerful appeal so many years ago to a throng estimated at 250,000.
Another activist with vivid memories of that August day in 1963 was Rep. John Lewis, D-Ga., who helped organize the march.
"I was here 40 years ago, 23 years old, a few pounds lighter, with all of my hair," he said, as he asked young and old alike to do more. "Too many of us are too complacent, too satisfied. We need to make a little noise."
"The focus of that day was a promise, the promise of equal protection under the law for all citizens, the promise of equal access to education," Rev. Jesse Jackson said in an interview with The Associated Press, on the Mall. "The promises of evening the playing field have been broken."
Indeed, as CBS News Correspondent Thalia Assuras notes, "Today, critics charge, much still needs to change. Blacks describe an undercurrent of racism, and four out of five say they don't get the same job opportunities as whites."
Before the speeches, participants took shelter from the bright sun under about a half dozen white tents set up for a series of teach-ins.
The panel discussions varied from education, economic justice and jobs to voter education and empowerment - which was one of the central themes of the weekend remembrance.
The coalition of about 100 diverse groups who organized the rally used the event to kick off a 15-month voter mobilization campaign.
Saturday's teach-ins and speeches culminated a two-day celebration of the march in which King issued his famous demand for justice for all, delivered on Aug. 28, 1963.
"I have a dream that one day this nation will rise up and live out the true meaning of its creed: 'We hold these truths to be self-evident, that all men are created equal,"' he said.
"I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character."
Organizers reached out this year to the younger generation of 20- to 30-year-olds, and many of them turned out.
Jimmy Prude, 20, a senior at Howard University, said he wanted to understand a little more about economic empowerment.
"I just want to see people be able to help better themselves, and be able to learn how to invest their money," he said. "All the skills that are needed to be successful in life."
Some people waiting for the rally waved American flags while others carried placards with the peace symbol and protested the war in Iraq.
King III, now 45, said he hoped that people who visit the inscription at the memorial will not only remember his father's call for justice and equality, but also realize "the work is nowhere near complete."
Jackson, though, said the Bush administration had instituted a "closed-door policy" that put up "very stiff resistance." He said current policies were anti-civil rights and anti-labor.
Among others in attendance were 60 people on the Poor People's March for Economic Human Rights who left Mississippi on Aug. 2 and arrived in Washington Saturday.
Protesters marched in single file, chanting, beating drums and waving American flags.
"We're trying to raise our voices and let the poor be heard," said marcher Nina Swanson. "It's tough because we're a poor group, so we're under-resourced and underfunded, and we just have our voices and our bodies."
On Friday, civil rights activists commemorated King's speech on the granite steps of the Lincoln Memorial, from where he addressed a March on Washington crowd of about 250,000 on a hot day four decades ago.
Coretta Scott King, stood on the steps of the memorial Friday as officials uncovered the words chiseled into the granite of a landing. "The inscription adds a sense of wholeness to this spot," she said.
About 1,000 people attended the ceremony, kicking off two days of observances tied to the March on Washington. A children's hip-hop choir performed and religious leaders led prayers during a vigil.
The inscription, over 2 feet wide, reads:
"I have a dream
Martin Luther King Jr.
The March on Washington
For jobs and freedom
August 28, 1963."
Organizers credited Thomas Williams of Louisville, Ky., who is white, with coming up with the idea of permanently embedding King's words on the memorial when he visited Washington with his wife in 1997.
"I looked for the spot where Martin Luther King stood and I couldn't find it," he said Friday, back in Washington to see his wish come true. Williams wrote to his member of Congress, Republican Anne Northrup, and she pushed legislation providing for the inscription.
Eleanor Holmes Norton, the District of Columbia's delegate to Congress, was a law student in 1963 who helped organize the march. She remembered his speech for its pragmatism as much as its poetry.
"His words were not art for art's sake," she said. "He was trying to win converts."