Obama said the change benefited not just African-Americans but also "women and Latinos, Asians and Native Americans, for Catholics, Jews and Muslims, for gays, for Americans with disabilities."

However, the president said, economic inequality not only remains but has worsened.

"There are successes in black America that would have been unimaginable 50 years ago ... but the gap in wealth between the races has grown," he said.

Equality "was not and never has been whether the doors of opportunity are cracked a bit wider for a few. It's whether our economic system provides a fair shot for the many, for the black custodian and the white steelworker, the immigrant dishwasher and the Native American veteran," he said.

Wednesday's ceremony featured speeches by Vice President Joe Biden and former Presidents Bill Clinton and Jimmy Carter.

Clinton said King's speech and the 1963 changed America.

"They opened minds," he said. "They melted hearts."

Clinton said progress requires that people "stop complaining and put our shoulders against the stubborn gates holding the American people back."

Carter said King would not have supported voter ID laws being passed in many states "to exclude certain voters, especially African-Americans."

The anniversary is a reminder racial disparities persist, senior Obama adviser Valerie Jarrett said in a White House blog.

"As we mark this important anniversary, we reflect on what the civil rights movement has meant for the country," she said.

Perhaps most important, she said, is to reflect on "the hard work that lies ahead as we continue to pursue the ideals laid out by Dr. King, and sought by the hundreds of thousands of Americans who marched through our nation's capital 50 years ago."

Despite many social advances, the economic disparities separating blacks and whites remain as wide as they were when marchers assembled on the National Mall in 1963.

"Certainly, poverty has declined for everybody, but it has declined in a way that the proportion of blacks to whites who are poor is about the same as it was 50 years ago," Duke University economics, public policy and African-American studies Professor William Darity Jr. told The Washington Post.

In politics, blacks are now elected to lead big cities and they make up a growing share of the U.S. House of Representatives. But few blacks have been elected to the Senate and governors offices, the Joint Center for Political and Economic Studies research organization says.

Senate and state house seats are viewed as natural springboards to the presidency and vice presidency, The Wall Street Journal said.

Still, the March on Washington for Freedom and Jobs, one of the largest political rallies for human rights in U.S. history, is widely seen as a turning point in the call for civil and economic rights for African-Americans.

The march -- 100 years after President Abraham Lincoln's Emancipation Proclamation -- is widely credited with helping pressure Congress to pass the Civil Rights Act of 1964 and the Voting Rights Act of 1965.

The U.S. Supreme Court struck down a key Voting Rights Act provision in June. Obama has called that ruling a setback.

The list of speakers also included members of King's family and U.S. Rep. John Lewis, D-Ga., the last surviving member of the original "Big Six" civil rights leaders who organized the 1963 march.

Oprah Winfrey and Oscar-winning actors Forrest Whittaker and Jamie Foxx also spoke.

Gospel singer BeBe Winans, country and pop singer LeAnn Rimes, contemporary Christian singer-songwriter Natalie Grant performed -- as did folk singers Peter Yarrow and Paul Stookey, whose group Peter, Paul and Mary performed at the 1963 march.

The event began with an interfaith service at the Martin Luther King Jr. Memorial on the mall at 9 a.m.

The Martin Luther King Jr. Center for Non-violent Social Change organized Wednesday's event.