History is replete with signal moments. For Americans, the March on Washington for Jobs and Freedom in 1963 is one of them.

Wednesday is the 50th anniversary of the march, a gathering of 250,000 people on the National Mall demanding, among other things, an end to segregation and racial discrimination. Culminating the rally, the Rev. Martin Luther King Jr. delivered his most famous speech.

"I have a dream that one day this nation will rise up, live out the true meaning of its creed: 'We hold these truths to be self-evident, that all men are created equal,'" he said from the steps of the Lincoln Memorial.

Newspaper editorials condemned the march, warning that it could turn violent. President John F. Kennedy, a civil rights supporter, worried about a backlash.

Instead, King's speech captured the nation's attention, and the march became an enduring image of the civil rights era.

But it was just a step in a continuing journey to King's promised land. Resistance to civil rights remained strong and, at times, violent.

Almost a year passed before the Civil Rights Act of 1964 was enacted, and only after debates marked by harsh denunciations of integration and a Senate filibuster that lasted 90 days. Yet another year went by before the Voting Rights Act became law.

Along the way, four young girls died in a bombing at a church in Birmingham, Ala., and three men working on a voter registration campaign disappeared in Mississippi. Their bodies were later found buried in an earthen dam.

Five decades later, progress is undeniable. Jim Crow is history. So are bombings and lynchings. Schools and other public facilities are integrated. Universities defend diversity, not segregation. Barack Obama is president.

Yet minorities are still more likely to be born in poverty and experience unemployment. Public schools may be desegregated, but quality isn't equal. And there's a renewed attack to voting rights.

In the pre-civil rights era, states imposed poll taxes and literacy tests to keep blacks from voting. The new tools are gerrymandering and restrictive ID laws.

Academic researchers and law enforcement investigators have shredded claims of widespread voter fraud. What can't be denied is this: Those most likely to lack a drivers license or other government-issued ID are the poor, a group that includes an inordinate share of minorities.

In the two months since the U.S. Supreme Court invalidated a key enforcement section of the Voting Rights Act of 1965, states from North Carolina to Texas revived laws previously blocked by the U.S. Justice Department. They have drawn new legislative and congressional districts that disadvantage minorities, imposed restrictions on early voting and voter registration drives and approved concealed-weapons permits while rejecting student ID cards to cast a ballot.

If he could look back 50 years later, King probably would recognize much of his dream. Unless Congress restores the Voting Rights Act, he also would see a nation marching back in time.