It has been a quarter-century now since a 34-year-old Martin Luther King Jr. stepped to a microphone at the Lincoln Memorial, the final speaker in a long, hot afternoon.

Fourteen minutes later, the minister from Atlanta was the unquestioned king of a movement, a movement that changed America forever. And his "I Have a Dream" speech entered history.It was no surprise that King could deliver a rousing sermon or a speech - at least no surprise to anyone who had heard him before.

And it was no accident that he was the last of 10 speakers on Aug. 28, 1963 - closing the show, as it were, at the mammoth rally culminating the March on Washington for civil rights.

King, introduced by labor leader A. Philip Randolph as "the moral leader of the nation," had been well known ever since leading a bus boycott by blacks in segregated Montgomery, Ala., in 1955.

On that Wednesday afternoon, 200,000 people - more than any in the movement had dared hope for - watched at the memorial. Millions more watched on television.

Excited, aware of just what it all meant, King delivered a speech for the ages, making up the best parts as he went along.

"It will be a long time," James Reston wrote the next day in The New York Times, "before (Washington) forgets the melodious and melancholy voice of the Rev. Dr. Martin Luther King Jr., crying out his dreams to the multitude. . . . `I have a dream,' he cried, again and again."

That's how it has come to be known: The Dream Speech.

"I have a dream," King sang. "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.' "

It was, just about everyone seemed to agree, the greatest part of a great American oration.

And it wasn't in the script.

"It was something he had done in Detroit a couple of weeks before," recalled Andrew Young, now Atlanta's mayor, then King's special assistant. "It was spontaneous in Detroit, and then he refined it in Washington. It didn't get any publicity in Detroit."

King obviously liked the theme, thought it worked well, thought it said something. But on that Wednesday afternoon, there was not to be time to say everything he wanted to say. Each of the 10 speakers was limited to eight minutes.

"There's no way in the world, Martin, that you can say what needs to be said in eight minutes," aide Walter Fauntroy told him the day before, as quoted by King biographer Stephen B. Oates. "They can't limit you - the spokesman of the movement - to that," said Fauntroy, now the congressional delegate representing the nation's capital.

"But they'll all be mad at me if I speak longer," King worried.

"Everybody was putting pressure on everybody to be brief," Young recalled in an interview last week. "He was trying to cut down his speech."

The night before, King, Young and other movement leaders gathered at Washington's Willard Hotel. They exchanged suggestions for the speech, with King writing it, his secretary typing it and retyping it, and King scribbling still more changes in the margins.

"He stayed up all night," Young said. "You'd look in the margin and see as many as four or five different words in one place, where he'd crossed it out, selected another one. He was much more particular about the language than he'd ever been before."

What Young remembers most from that all-night labor of language is a theme that came early in the speech, contrasting Abraham Lincoln's emancipation of the black man with the black man's place in 1963 America.

"In a sense," King wrote, "we've come here to our nation's capital to cash a check . . . a promissory note . . . a promise that all men - yes, black men as well as white men - would be guaranteed the unalienable rights of life, liberty and the pursuit of happiness . . .

"America has given the Negro people a bad check, a check which has come back marked `insufficient funds.' But we refuse to believe that the bank of justice is bankrupt."

On that Wednesday, King sailed through his speech, through the bad-check analogy, sticking to his text. But as tens of thousands clapped and cheered, as his closest aides encouraged him - "All right! Tell it!" - he suddenly decided to keep going.

He remembered what he had said in Detroit, and his eight-minute speech became 14.

Almost immediately, the speech was acclaimed as a milestone.

It still electrifies. MPI Home Video of Chicago, which sells the speech on videotape for $14.95, reports that it's one of the company's best sellers, with 10,000 sold so far and sales still going strong.

Memories of the day will be rekindled on Saturday in a march on Washington marking the 25 years since the original rally.

But those closest to King knew back then the power of his words. "We figured we heard that every time he spoke," Young said. "There was nothing new about his oratory."

According to some, he even got better still. Young picks King's 1967 speeches against the Vietnam War as his finest. He was at his best, Young said, when he just let it go.

"The speeches he gave almost totally from the heart were better than the speeches he prepared - or the ones other people tried to prepare for him," Young said.

"They were just things he felt real deeply, thought through very deeply. There was a natural eloquence about him. He would be eloquent in conversation, just go up on these flights of oratory."

`I Have a Dream' highlights

"I say to you today, my friends, so even though we face the difficulties of today and tomorrow, I still have a dream. It is a dream deeply rooted in the American dream.

"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.'

"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.

"So let freedom ring from the prodigious hilltops of New Hampshire; let freedom ring from the mighty mountains of New York; let freedom ring from the heights of the Alleghenies of Pennsylvania; let freedom ring from the snow-capped Rockies of Colorado; . . . from every mountainside, let freedom ring."