There are places and moments in America where this nation’s destiny has been decided.

Selma is such a place. In one afternoon 50 years ago, so much of our turbulent history — the stain of slavery and anguish of civil war; the yoke of segregation and tyranny of Jim Crow; the death of four little girls in Birmingham; and the dream of a Baptist preacher — all that history met on this bridge.

It was not a clash of armies, but a clash of wills; a contest to determine the true meaning of America. And because of men and women like John Lewis, Joseph Lowery, Hosea Williams, Amelia Boynton, Diane Nash, Ralph Abernathy, C.T. Vivian, Andrew Young, Fred Shuttlesworth, Dr. Martin Luther King, Jr., and so many others, the idea of a just America and a fair America, an inclusive America, and a generous America — that idea ultimately triumphed.

We gather here to celebrate them. We gather here to honor the courage of ordinary Americans willing to endure billy clubs and the chastening rod; tear gas and the trampling hoof; men and women who despite the gush of blood and splintered bone would stay true to their North Star and keep marching towards justice.

What they did here will reverberate through the ages ... because they proved that nonviolent change is possible, that love and hope can conquer hate.

Selma is not some outlier in the American experience. It is instead the manifestation of a creed written into our founding documents: “We the People...in order to form a more perfect union.” “We hold these truths to be self-evident, that all men are created equal.”

These are not just words. They’re a call to action, a roadmap for citizenship and an insistence in the capacity of free men and women to shape our own destiny.

It’s the idea held by generations of citizens who believed that America is a constant work in progress; who believed that loving this country requires more than singing its praises or avoiding uncomfortable truths.

Because of campaigns like this, a Voting Rights Act was passed. Political and economic and social barriers came down. And the change these men and women wrought is visible here today in the presence of African Americans who run boardrooms, who sit on the bench, who serve in elected office from small towns to big cities; from the Congressional Black Caucus all the way to the Oval Office.

Because of what they did, the doors of opportunity swung open not just for black folks, but for every American. Women marched through those doors. Latinos marched through those doors. Asian Americans, gay Americans, Americans with dis- abilities — they all came through those doors.

What a glorious thing, Dr. King might say. And what a solemn debt we owe. Which leads us to ask, just how might we repay that debt?

First and foremost, we have to recognize that one day’s commemoration, no matter how special, is not enough. If Selma taught us anything, it’s that our work is never done ... that action requires that we shed our cynicism. For when it comes to the pursuit of justice, we can afford neither complacency nor despair.

We do a disservice to the cause of justice by intimating that bias and discrimination are immutable, that racial division is inherent to America. If you think nothing’s changed in the past 50 years, ask somebody who lived through the Selma or Chicago or Los Angeles of the 1950s. Ask the female CEO who once might have been assigned to the secretarial pool if nothing’s changed. Ask your gay friend if it’s easier to be out and proud in America now than it was thirty years ago.

Of course, a more common mistake is to suggest that ... racism is banished. We don’t need the Ferguson report to know that’s not true. We just need to open our eyes, our ears and our hearts to know that this nation’s racial history still casts its long shadow upon us.

If we want to honor the courage of those who marched that day, then all of us ... need to recognize as they did that change depends on our actions, on our attitudes, the things we teach our children. And if we make such an effort, no matter how hard it may sometimes seem, laws can be passed, and consciences can be stirred and consensus can be built.

With such an effort, we can make sure our criminal justice system serves all and not just some. Together, we can raise the level of mutual trust that policing is built on. Together, we can address unfair sentencing and overcrowded prisons, and the stunted circumstances that rob too many boys of the chance to become men.

With effort, we can roll back poverty and the roadblocks to opportunity. Yes, we can make sure every child gets an education suitable to this new century. We can make sure every person willing to work has the dignity of a job and a fair wage.

And with effort, we can protect the foundation stone of our democracy for which so many marched across this bridge — the right to vote. In 2015, there are laws across this country designed to make it harder for people to vote. Meanwhile, the Voting Rights Act, the culmination of so much blood, so much sweat and tears, the product of so much sacrifice ... stands weakened, its future subject to political rancor.

One hundred members of Congress have come here today to honor people who were willing to die for the right to protect it. If we want to honor this day, let that hundred go back to Washington and gather four hundred more, and together, pledge to make it their mission to restore that law this year. That’s how we honor those on this bridge.

If every new voter-suppression law was struck down today, we would still have, here in America, one of the lowest voting rates among free peoples. Fifty years ago, registering to vote here in Selma and much of the South meant guessing the number of jellybeans in a jar, the number of bubbles on a bar of soap. It meant risking your dignity, and sometimes, your life.

What’s our excuse today for not voting? How do we so casually discard the right for which so many fought? How do we so fully give away our power, our voice, in shaping America’s future?

Fifty years from Bloody Sunday, our march is not yet finished, but we’re getting closer. Our job’s easier because somebody already got us through that first mile. Somebody already got us over that bridge. When it feels the road is too hard, when the torch we’ve been passed feels too heavy, we will remember these early travelers, and draw strength from their example.

We honor those who walked so we could run. We must run so our children soar. And we will not grow weary. For we believe in the power of an awesome God, and we believe in this country’s sacred promise.

May He bless those warriors of justice no longer with us, and bless the United States of America.