(CNN) Fifty years ago this weekend, a 25-year-old John Lewis was beaten so badly by Alabama state troopers that they fractured his skull.

Lewis calls the Edmund Pettus Bridge -- where the troopers and and a group of white men deputized into a posse by the sheriff attacked hundreds of peaceful protesters on Bloody Sunday, March 7, 1965 -- an "almost holy place."

Now a Democratic U.S. congressman, Lewis is returning to Selma -- as he has nearly every year since that historic march -- to remember the fight for voting rights and to push voters across the country to participate in the political process. He also wants people to continue to speak up about the problems of racial injustice and poverty that persist in American society.

"It is important to come back to remember Selma," Lewis told CNN in an interview at First Baptist Church. "The vote is powerful. It is the most powerful nonviolent tool we have in a democratic society and I don't want people to forget that people paid a price.

"Selma, these churches and these people, gave it everything they had. We wouldn't be where we are today as a nation and as a people (if it) hadn't been for this community."

Churches -- like Selma's First Baptist and Brown Chapel -- served as important meeting places during the movement, in part because they were run by the black community.

The solidarity of music

And music was vital as a unifying force.

"Without music, the movement would have been like a bird without wings," Lewis said.

He recalled how people would often sing during the marches, sometimes making up songs along the way.

"Music helped create a sense of solidarity, and there were people in some communities, in some towns and cities like Selma, saying if the meetings are being held at the church, it must be all right. That's the house of the Lord. They must be doing something that is right."

Activists had been working for years in and around Selma trying to help people register to vote. At the time, only 2.1% of blacks in Dallas County were registered, Lewis said. When blacks attempted to register, they were often given impossible tasks, like counting the number of jelly beans in a jar or the number of bubbles on a bar of soap, to complete before being allowed to sign up. Black lawyers, doctors, business people, public school teachers and college professors were told they could not read and write well enough to pass the so-called literacy test.

As chairman of the Student Nonviolent Coordinating Committee, Lewis -- along with many others -- would spill blood to change that, not only as a leader of the Bloody Sunday march but in other confrontations across the South.

A fateful moment for the movement

Lewis was arrested some 40 times during the 1960s as he challenged the segregationist Jim Crow laws that kept blacks oppressed. He spent 44 days imprisoned in Mississippi during the Freedom Rides in 1961. As a student at Fisk University, he organized sit-ins at lunch counters in Nashville, Tennessee, even spending his birthday in jail there in 1961 -- so Lewis was no stranger to run-ins with the law. But the events of Bloody Sunday would prove fateful for the movement.

Television cameras and photographers captured the troopers attacking the marchers with night sticks and whips -- one man in the posse even had a rubber hose wrapped with barbed wire, Lewis wrote in his memoir "Walking with the Wind."

The troopers trampled the crowd with their horses and released nauseating tear gas. The pictures horrified citizens across the country. Eight days after the march, President Lyndon B. Johnson spoke before Congress about voting rights. He signed the Voting Rights Act on Aug. 6 to ensure that all citizens would be able to vote regardless of their skin color.

Five decades later, Lewis said a great deal of progress has been made in the struggle for equality. But he added that, despite having twice elected a black man to the nation's highest office, the country still has a long way to go to become the so-called "Beloved Community" Dr. Martin Luther King Jr. envisioned "where we can lay down the burden of race."

"We have a black president. We've made a lot of progress, but we're not a post-racial society yet," he said. "We still have a distance to go. The scars and stains of racism are still deeply embedded in the American society."

The need for 'righteous indignation'

Lewis, who has written a trilogy of graphic novels for young adults about his life called "March," said it was important not to sweep the problems that still plague America under the rug and to instead speak up with a sense of "righteous indignation."

"You cannot be quiet. You have to speak up. You have to speak out. You have to find a way to get in the way and make some noise," he said, referring in particular to the killings of unarmed black men by police last summer in Ferguson, Missouri, and New York City.

He urged those demonstrating against police brutality and racial injustice to study and model the nonviolent methods of the civil rights activists of the 1950s and '60s.

The poverty affecting people of all races across the country still gnaws at Lewis, as does a lack of access to a good education. He believes people should be outraged about hunger and violence, and fired up to renew and strengthen the Voting Rights Act after a 2013 Supreme Court ruling gutted the key provision requiring certain states with a history of racial discrimination at the polls to "pre-clear" any changes to voting laws with the federal government before implementing them.

A bipartisan commemoration

On Saturday, Lewis and nearly 100 members of Congress from both parties will join President Barack Obama at the bridge in Selma -- a bridge that still bears the name of a Confederate general who was also a Ku Klux Klan leader -- to mark the 50th anniversary of Bloody Sunday. The bipartisan event comes as efforts to update to the Voting Rights Act have stalled in Congress. Still, Lewis is optimistic both parties can come together to fix it.

"We must do it. It's the right thing to do," he said. "There is a deliberate, systematic effort to take us back. We've made too much progress to go back." He was referring to efforts in some states to do away with early voting and voting on Sunday or on weekends and to require photo IDs, moves he said make it harder for young people, seniors and minorities to vote.

"I'm afraid that if we fail to fix it, many of our fellow citizens will not be able to become participants in the democratic process," he concluded.