A week after Bloody Sunday, President Johnson addressed a joint session of Congress in a live televised event, imploring the passage of a voting rights act:

"We cannot, we must not, refuse to protect the right of every American to vote in every election that he may desire to participate in. And we ought not and we cannot and we must not wait another 8 months before we get a bill. We have already waited a hundred years and more, and the time for waiting is gone ...

But even if we pass this bill, the battle will not be over. What happened in Selma is part of a far larger movement which reaches into every section and state of America. It is the effort of American Negroes to secure for themselves the full blessings of American life. Their cause must be our cause too. Because it is not just Negroes, but really it is all of us, who must overcome the crippling legacy of bigotry and injustice. And we shall overcome."

Later that month, King and other leaders of the movement successfully led thousands of marchers from Selma to the state capitol in Montgomery, protected along the way by the National Guard on Johnson's orders. By August 1965, just five months after Bloody Sunday, Johnson had signed the Voting Rights Act, one of the most significant pieces of civil rights legislation in U.S. history.

The law banned discriminatory voting practices, authorizing the deployment of federal election monitors and requiring specific states and counties with a history of discrimination to seek explicit approval from the Justice Department before making any changes in local election rules.

The results were dramatic and immediate: More than 27,000 African-Americans in Alabama, Louisiana and Mississippi successfully registered to vote in the first three weeks after the law's passage. Within the first two years, In Mississippi alone, registration among eligible black voters jumped from 6.7 percent of the state's eligible black voters to nearly 60 percent.

History, though, rarely comes packaged in neatly wrapped happy endings. And celebrated rights, no matter how hard they've been fought for, tend to erode if not vigilantly defended.

In 2013, the Supreme Court struck down the heart of the Voting Rights Act. The court's conservative majority ruled that the time's had changed and the law's safeguards were no longer necessary. The decision stripped the law of its primary enforcement mechanism requiring federal oversight of jurisdictions with a history of voter discrimination -- including most of the South.

Almost immediately after the decision, Texas and North Carolina, freed from restrictions, introduced controversial voter photo ID legislation. Many of the other previously monitored states have followed suit, enacting laws restricting voting access, including strict voter ID requirements and limitations on early voting and absentee ballots.

Although conservative proponents defend the new rules as necessary in preventing voter fraud, the changes have a disproportionately negative impact on poor, minority voters who are more likely lack photo identification and often depend heavily on more flexible voting options.

During the ceremonies in Selma this weekend, a succession of speakers beseeched the nation to wage a renewed battle for voting rights protections as the best way to honor the legacy of the protesters who risked their lives half a century ago.

"We have witnessed over the last few years, the worst assault on voting rights since the Voting Rights Act was passed in 1965," Rev. Raphael Warnock, of Ebenezer Baptist Church in Atlanta, told USA Today. "Come this weekend we'll see a parade of politicians make their way to Selma. Our message to those politicians is that you cannot celebrate the lessons of history while sitting on the wrong side of history."

Obama echoed this sentiment in his address Saturday in front of the Edmund Pettus Bridge.

"Right now, in 2015, 50 years after Selma, there are laws across this country designed to make it harder for people to vote," he said. As we speak, more such laws are being proposed. Meanwhile, the Voting Rights Act, the culmination of so much blood, so much sweat and tears, the product of so much sacrifice in the face of wanton violence, stands weakened, its future subject to political rancor. How can that be? The VRA was one of the crowning achievements of our democracy, the result of Republican and Democratic efforts ... If want to honor this day (let Congress) pledge to make it their mission to restore that law this year. That's how we honor those on this bridge."

Obama also criticized the strikingly low rate of voter turnout across the country in recent years.

"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 people," he added. "What's our excuse today for not voting? How do we so causally discard the right for which so many fought. How do we so fully give away our power, our voice in shaping America's future?"

Gov. Robert Bentley of Alabama, a Republican, also spoke on Saturday, noting that he hoped the occasion would show how much Alabama had changed since those tumultuous days.

“We want people in America and the world to realize that Alabama is a different place and a different state than it was 50 years ago,” Bentley told the New York Times. “It has become probably as much of a colorblind state as any state in the country, and we’re very proud of the advancement we've made.”

The stats suggest otherwise.

Alabama began enforcing strict voter photo ID rules last year. The state is one of the poorest in the nation. More than 30 percent of black and Latino residents live in poverty. Meanwhile, the state and its school systems remain starkly segregated.

Take Selma. In 1965, the city's population was nearly evenly divided. But after a half century of white flight, about 80 percent of its 20,000 residents today are black and the town's infrastructure is literally crumbling.

However, the Selma Country Club still does not have a single black member, the Washington Post reports.

Dallas County, where Selma is located, was ranked poorest in the state last year, with one of the highest child poverty rates in the nation and unemployment hovering above 10 percent -- almost twice the national average. 40 percent of Selma's families, and about two-thirds of its children, live below the poverty line, with a violent crime rate roughly five times the state average, according to U.S. Census figures.

Early in his speech on Saturday, Obama noted these persistent disparities. Although praising the tremendous gains in equality that have come about as a result of the sacrifices demonstrators here made 50 years ago, the president rejected the notion that racism has been defeated.

“We don’t need the Ferguson report to know that’s not true,” he said. “We just need to open our eyes and our ears and our hearts to know that this nation’s racial history still casts its long shadow upon us. We know the march is not yet over. We know the race is not yet won. We know reaching that blessed destination where we are judged, all of us, by the content of our character requires admitting as much, facing up to the truth.”

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50 Years after "Bloody Sunday," Still Miles to Go in March for Voting Rights