John Robert Lewis died at age 80 after a battle with cancer. Rev. Cordy Tindell "C.T." Vivian died at age 95 of natural causes.
Both men were the epitome of "good trouble" -- Lewis' favorite saying and approach to confronting injustices guided by his belief in nonviolence. They worked alongside the Rev. Martin Luther King Jr. in the forefront of the historic struggle for racial justices in the 1960s.
At the time, their bloody beatings during protests shocked the nation and galvanized support that led to key changes in the fight for equality. For their years of arrests, confrontations and unyielding demands for justice, they received the highest civilian honor from the nation's first Black President.
John Robert Lewis
John Lewis was more than an icon of the civil rights movement. He was also a beloved Georgia congressman, a political force and an ally for marginalized communities nationwide.
"Today, America mourns the loss of one of the greatest heroes of American history: Congressman John Lewis, the conscience of the Congress," House Speaker Nancy Pelosi said in a statement.
Lewis, a Democrat who served as the US representative for Georgia's 5th congressional district for more than three decades, was considered a moral conscience of Congress because of his belief in a nonviolent fight for civil rights.
His passion for equal rights was backed by a long record of action that included dozens of arrests during protests against racial and social injustice.
A follower and colleague of Martin Luther King Jr., he participated in lunch counter sit-ins, joined the Freedom Riders in challenging segregated buses and -- at the age of 23 -- was a keynote speaker at the historic 1963 March on Washington.
"We do not want our freedom gradually; we want to be free now," he said at the time.
"Sometimes when I look back and think about it, how did we do what we did? How did we succeed? We didn't have a website. We didn't have a cellular telephone," Lewis has said of the civil rights movement.
At age 25, he also helped lead a march for voting rights on the Edmund Pettus Bridge in Selma, where he and other marchers were met by heavily armed state and local police who attacked them with clubs, fracturing Lewis' skull.
Images from that "Bloody Sunday" shocked the nation and galvanized support for the Voting Rights Act of 1965, signed into law by President Lyndon B. Johnson.
In 2011, after more than 50 years on the front lines of the civil rights movement, America's first Black President placed the Presidential Medal of Freedom on his neck.
Lewis has described attending President Barack Obama's 2009 inauguration as an "out-of-body" experience.
Cordy Tindell Vivian
C.T. Vivian was also a major force in the civil rights movement. He worked alongside King and the Southern Christian Leadership Conference in the struggle for racial equality.
And like Lewis, he was also part of the Freedom Riders -- civil rights activists who rode through southern states to make sure bus terminals and other public facilities were not segregated.
His civil rights actions started decades ago with his first nonviolent protest in 1947 -- a lunch counter sit-in in Peoria, Illinois.
Vivian had a strong religious upbringing and he and other ministers founded the Nashville Christian Leadership Conference, an affiliate of the Southern Christian Leadership Conference. The group helped organize sit-ins and civil rights marches.
Some of the marches ended in violence against him. He once led a group of people to register to vote in Selma, Alabama, despite defiance by a local sheriff who blocked the group.
"We will register to vote because as citizens of the United States we have the right to do it," he told the sheriff. The sheriff responded by beating Vivian until blood dripped off his chin in front of rolling cameras. The images helped galvanize wider support for change.
Vivian also created a college readiness program to help care for children kicked out of school for protesting racism.
The US Department of Education used his program as a guide to create Upward Bound, which was designed to improve high school and college graduation rates for students in underserved communities.
In the late 1970s, Vivian founded an anti-racism organization that focused on monitoring the Ku Klux Klan.
CNN's Kelly McCleary, Lauren Fox and Brandon Griggs contributed to this report.