It was a violent time with violent prospects.

But instead of rage and fury, he gave America a dream.

Forty years ago today in Washington, 17,000 combat-ready troops prepared for what only seemed inevitable. Stores closed and chain-locked their doors; Washington's Archbishop Patrick O'Boyle told his nuns to stay inside for fear of rioting in the streets.

More than 250,000 people gathered for the "March on Washington for Jobs and Freedom." The nation braced for a backlash.

The country was in the midst of a racial nightmare: In the summer of 1963, many states still operated segregated school districts; less than 10 percent of African-Americans in the South's 100 largest counties were registered to vote; in many places, blacks could not even serve on juries.

That spring, in Birmingham, Ala., police commissioner Bull Connor turned his dogs on peaceful demonstrators.

On May 28, the Jackson, Miss., home of Medgar Evers, state field secretary for the NAACP, was firebombed. Two weeks later, he was assassinated in front of his home.

In Danville, Va., civil rights workers faced fire hoses; in Americus, Ga., police beat peaceful protestors; in Winona, Miss., police arrested Fannie Lou Hamer because she attended a voter registration workshop - they took her to jail, beat her and plotted to drown her in a river.

Late on the afternoon of Aug. 28, the Rev. Martin Luther King Jr., the son of a Baptist preacher, braced himself at the podium on the steps of the Lincoln Memorial and, for a moment, paused and glanced heavenward.

"I have a dream," he cried. "It is a dream deeply rooted in the American dream."

Today his speech - often repeated, memorialized, recently enshrined in granite on the steps from which he spoke - is considered one of the nation's sacred texts, a primary document of the American faith.

The words, which no doubt will be repeated countless times today in schools and government halls, on radio and television nationwide, have gradually taken a place alongside the Gettysburg Address, Abraham Lincoln's Second Inaugural and John F. Kennedy's 1961 Inaugural as a rightful part of the American canon.

"It certainly fits in that pantheon of great civic addresses," said Richard Lischer, Duke University professor and author of The Preacher King: Martin Luther King, Jr., and the Word that Moved America. "But it also performed the function of a sermon on a national scale - in fact, on an unparalleled scale in American history."

With its biblical allusions and resonances, delivered by a man with a powerful, preacherly countenance, imbued with dramatic inflections and carried by a roiling baritone voice, the speech, Lischer said, "served to call America to a higher view of itself and, implicitly, back to a deeper understanding of God and its own history."

That a religious speech could so profoundly touch a secular nation may seem peculiar today. That at the time of King's death, in April 1968, the speech had all but vanished from national memory and was rarely referenced by people in the civil rights movement may seem unimaginable. That it spawned debate, controversy and reinterpretation from the day the words were uttered makes it all the more mystifying.

But like the Constitution, Declaration of Independence and other foundational documents of the American creed, the speech, widely known for its "Dream" refrain, is now recognized as a kind of living entity.

"That's why I refer to it as a 'sacred' text," said Drew Hansen, author of the recently published book The Dream: Martin Luther King Jr. and the Speech That Inspired a Nation. "People use the words of these primary documents the way they would an authoritative religious text: It expresses the beliefs of their community of faith and provides guidance for how to live and inspiration for how to move forward to the future. It also happens to be why people sometimes argue over it and interpret it in different ways, just like they do with, say, the Bible or the Constitution."

It is a speech with a past, a story and a national audience that, especially on this day, often stops to ponder the magic of a few well-chosen words.

The words "I have a dream" never appeared in the written version King intended to deliver that day. The piece he carefully crafted over four days before Aug. 28 highlighted a theme he referred to as the "bad check." He had hoped that by reflecting on the centennial of the Emancipation Proclamation of 1863, he could demonstrate how the country failed its "sacred obligation" to black Americans for 100 years - a "bad check; a check which has come back marked 'insufficient funds.' " Echoing Lincoln ("Five score years ago ... " the speech began), King wanted to stress two themes: the economic plight of blacks, the demand for civil rights legislation.