On April 4, 1968, an assassin took the life of Martin Luther King Jr. He was 39 years old. Forty years after his death, Americans honor King with a national holiday celebrated on the third Monday of each January. Above, DJ Lewis (left) and his father, Dennis Sr., join in a January 2006 march in honor of King in Oklahoma City.

Washington -- On April 4, 1968, in Memphis, Tennessee, an assassin’s bullet took the life of Martin Luther King, the main architect and the leader of the nonviolent civil rights movement in the United States. He was 39 years old. The medical examiners said King died with the heart of a 60-year-old, because he had for so long carried the burden of so many. Some 100,000 Americans stood outside the church at the time of his funeral.

The day before, as part of his “poor people’s campaign,” King was campaigning on behalf of striking -- and primarily black -- sanitation workers. His last address drew strongly on his lifelong study of the Bible. It would prove prophetic:

Well, I don’t know what will happen now; we’ve got some difficult days ahead. But it really doesn’t matter with me now, because I’ve been to the mountaintop. And I don’t mind. Like anybody, I would like to live a long life -- longevity has its place. But I’m not concerned about that now. I just want to do God’s will. And He’s allowed me to go up to the mountain. And I’ve looked over, and I’ve seen the Promised Land. I may not get there with you. But I want you to know tonight that we, as a people, will get to the Promised Land. And so I’m happy tonight; I’m not worried about anything; I’m not fearing any man. Mine eyes have seen the glory of the coming of the Lord.

The year 1968 was one of political upheaval throughout the world. In the United States, just two months later, on June 5, another assassin took the life of Senator Robert Kennedy, who as attorney general had provided timely assistance to civil rights activists.

DAYS OF ANGER

The murder of Martin Luther King sparked riots in Washington and more than 100 other American cities, threatening to turn a peaceful struggle of African Americans into a violent racial confrontation. Even before the tragic event, the movement seemed to be undergoing a transformation that many of King’s closest associates watched with apprehension.

By May 1966, Stokley Carmichael, veteran of numerous voter registration drives, had established himself as the new head of the Student Nonviolent Coordinating Committee (SNCC), the principal student organization of the civil rights movement, whose leadership was growing increasingly impatient with the gradualist strategy of Martin Luther King and his associates.

In a speech at Greenwood, Mississippi, Carmichael raised a call for “Black Power.” Where people like Thurgood Marshall and Martin Luther King had sought integration, Carmichael instead sought separation. Integration, he said, was “an insidious subterfuge, for the maintenance of white supremacy.”

Meanwhile, the Black Panther Party (some accounts trace the name to a visual emblem for illiterate voters used in an Alabama voter registration drive), founded in Oakland, California, in October 1966 by activists Huey P. Newton and Bobby Seale, employed armed members -- “Panthers” -- to shadow police officers who, they believed, unfairly targeted blacks.

While the party briefly enjoyed a measure of popularity, particularly through its social services programs, armed altercations with local police resulted in the death or jailing of prominent Panthers, turned many Americans against its violent ways, and fragmented the Panther movement. It petered out in a maze of factionalism and mutual recriminations.

Many feared, however, that King’s assassination would increase the influence of militant elements within the movement. At that time, some questioned King’s life work. But the “Promised Land” that King described was in many ways far closer than it seemed during the riots of April 1968.

AMERICAN CONSENSUS

The African-American historical experience will always be unique. But meaningful federal enforcement of the right to vote equipped black Americans with the tools that immigrants and other minority groups long have used to pursue -- and achieve -- the American Dream. In the United States, people who vote wield real political power. With the vote -- and over time -- legal and political equality for African Americans has produced gains in nearly every walk of life.

John R. Lewis, for example, was one of the Freedom Riders beaten bloody by a Montgomery, Alabama, mob in 1961. Today he represents Georgia’s 5th Congressional District in the U.S. House of Representatives. Nearly 50 of his congressional colleagues are African Americans, and several of them wield great political power as chairpersons of in?uential congressional committees.

In 1963, Denise McNair was among the girls killed when racist vigilantes bombed Birmingham’s Sixteenth Street Baptist Church. In 2005, her friend Condoleezza Rice took office as the nation’s secretary of state.

Black secondary school graduation rates have nearly tripled since 1966, and the rate of poverty has been nearly halved in that time. The expansion of the black middle class is a widely noted social development, as are the many successful entrepreneurs, scholars and literary and artistic achievers who are African American.

Although Americans continue to wrestle with issues of race, those issues differ profoundly from those addressed by Thurgood Marshall, Martin Luther King and the civil rights movement generation.

Unquestionably, the civil rights movement forced the American people to confront squarely the contradiction between their ideals and the reality of segregation and inequality. In doing so, it launched the nation far along the path to full racial equality, a road it is still traveling.

Probably the most important measure of progress is the emergence -- not least among the younger Americans who will build the nation’s future -- of a broad and deep consensus that the shameful histories of slavery, segregation and disadvantage must be relegated to just that: history.

The materials above are adapted from Free At Last: The U.S. Civil Rights Movement, a book to be published on America.gov during summer 2008.