CNN's Moni Basu reported from Selma. CNN's Slma Shelbayah wrote and reported from Atlanta. CNN's Steve Almasy and Douglas Brinkley contributed to this report.
Huge crowd walks in 'Bloody Sunday' march in Selma
"Our march is not yet finished. But we are getting closer," Obama said Saturday, his words echoing into a crowd of thousands lined up in front of him.
Obama emphasized that a day of commemoration is not enough to repay the debt paid by the marchers who were beaten 50 years ago as they demonstrated for voting rights.
"If Selma taught us anything, it's that our work is never done," the President said near Edmund Pettus Bridge.
The President said that what civil rights marchers did years ago "will reverberate through the ages. Not because the change they won was preordained; not because their victory was complete; but because they proved that nonviolent change is possible; that love and hope can conquer hate."
Obama: Revive the rights
He hailed the marchers as heroes.
The President said that "the Americans who crossed this bridge, they were not physically imposing, but they gave courage to millions. They held no elected office. But they led a nation."
The President called on Congress to restore the Voting Rights Act, first passed in 1965.
In 2013, the U.S. Supreme Court overturned a key provision of the law that required certain states with a history of racial discrimination at the polls to "pre-clear" any changes to the law with the federal government before implementing them.
Efforts to revive key provisions of the act have stalled in Congress.
Lewis: We must finish the work
Many of the nation's leaders, activists and celebrities were in Selma on Saturday attending various activities taking place in memory of the historic event.
On Saturday, Rep. John Lewis -- one of the demonstrators bloodied by troopers 50 years ago -- and nearly 100 other members of Congress from both parties joined the President at the bridge in Selma -- a bridge that still bears the name of Pettus, a Confederate general who was also a Ku Klux Klan leader.
"We must use this moment to recommit ourselves to do all we can to finish this work. There's still work to be done," said Lewis, adding this is an opportunity to "redeem the soul of America."
A city of two sisters
Reflecting a sense of change in the half century since "Bloody Sunday," and with Selma again in a national media spotlight, the mood in the crowd Saturday was of unity, and talks were focused on how to move America forward.
But some current Selma residents worried that after the dignitaries leave their town -- with a population 82% black and with more than 40% of its people living below the national poverty level -- will fade from view except for its historical significance.
Geraldine Martin, 59, has lived in Selma all her life. She was 9 years old on "Bloody Sunday" and with her mother had just welcomed a little sister, Belinda, to the world on that day. The two sisters grew up in Selma less than a decade apart.
Belinda left Selma after high school and now lives in Atlanta. Her view of Selma has changed over the years -- looking in from the outside.
"I don't see how Selma will move forward without togetherness," said Belinda. "There is no diversity in Selma. People don't live together."