SELMA, Ala. - Selma paid tribute Sunday to the late President Lyndon Johnson for the 1965 Voting Rights Act, recalling the clashes between police and marchers 50 years ago in this Alabama city that helped secure those equal voting protections.

Police beat and tear-gassed marchers at the foot of the bridge in Selma on March 7, 1965, in a spasm of violence that shocked the nation. The attack on demonstrators preceded the Selma-to-Montgomery march, which occurred two weeks later. Both helped build momentum for congressional approval of the Voting Rights Act that year.

Luci Baines Johnson accepted the award Sunday from Selma city officials on behalf of her father, saying it meant so much to her a half century later to see him honored for the landmark act.

"You remember how deeply Daddy cared about social justice and how hard he worked to make it happen," she told the crowd. Several hundred gave her a standing ovation and some chanted, "L.B.J., L.B.J."

She said what happened in Selma changed the world, adding that she witnessed the painful injustice of segregation as a child. She also recalled standing behind her father as he signed the act into law.

A march from Selma to Montgomery in remembrance of the journey is set to begin Monday morning and culminate with a rally at the Alabama Capitol on Friday afternoon.

Many had gathered for a unity breakfast, film screenings, and a planned pre-march rally starting Sunday afternoon at the foot of the Edmund Pettus Bridge, where President Obama spoke a day earlier. On Saturday, Obama touched on improvements in American race relations. He mentioned recent high-profile clashes between citizens and law enforcement.

"We just need to open our eyes, and ears, and hearts, to know that this nation's racial history still casts its long shadow upon us," Obama said. "We know the march is not yet over, the race is not yet won, and that reaching that blessed destination where we are judged by the content of our character requires admitting as much."

Obama was joined by others in the town of roughly 20,000 to hear speeches from leaders including Georgia Rep. John Lewis - an Alabama native who was among the demonstrators attacked by law officers on a march for equal voting rights.

The U.S Supreme Court in 2013 struck down section 4 of the Voting Rights Act which required states with a history of minority voter suppression to get permission from the Justice Department before changing voting laws.

The Rev. Al Sharpton, speaking at Sunday's unity breakfast, said the changes in voting laws threatened to push minority voters backward down the bridge.

"While we are celebrating, there are those that are trying to dismantle what we are celebrating," Sharpton said.