RELATED STORY: Congressman John Lewis, civil rights icon, dies at 80
Martin Luther King III: "John Lewis was an American treasure"
Martin Luther King III, the oldest son of civil rights leader Martin Luther King Jr, tweeted on the passing of John Lewis:
"John Lewis was an American treasure. He gave a voice to the voiceless, and he reminded each of us that the most powerful nonviolent tool is the vote. Our hearts feel empty without our friend, but we find comfort knowing that he is free at last."
Bill and Hilary Clinton: "We have lost a giant"
Former President Bill Clinton and Secretary of State Hillary Clinton have issued a tribute to John Lewis, saying: "We have lost a giant."
"John Lewis gave all he had to redeem America’s unmet promise of equality and justice for all, and to create a place for us to build a more perfect union together," the statement continued.
"From a small farm in Alabama, to life-risking service in the civil rights movement, to three decades in Congress, he was always 'walking with the wind,' steered by a moral compass that told him when to make good trouble and when to heal troubled waters. Always true to his word, his faith, and his principles, John Lewis became the conscience of the nation.
"Hillary and I loved John. We were blessed by his friendship, support, and wise counsel. We’ll miss him so much, but we’ll always be grateful to God for his long good life, and grateful that he lived to see a new generation of Americans take to the streets in search of his long sought 'beloved community.'
"Our hearts go out to his son John-Miles and the entire Lewis family, his able loyal staff, and all who loved and admired him the world over."
Nancy Pelosi: Lewis was "one of the greatest heroes of American history"
House Speaker Nancy Pelosi has called John Lewis "one of the greatest heroes of American history" and "the conscience of the Congress" in a statement mourning his passing.
“John Lewis was a titan of the civil rights movement whose goodness, faith and bravery transformed our nation – from the determination with which he met discrimination at lunch counters and on Freedom Rides, to the courage he showed as a young man facing down violence and death on Edmund Pettus Bridge, to the moral leadership he brought to the Congress for more than 30 years," she wrote.
“In the Congress, John Lewis was revered and beloved on both sides of the aisle and both sides of the Capitol. All of us were humbled to call Congressman Lewis a colleague, and are heartbroken by his passing. May his memory be an inspiration that moves us all to, in the face of injustice, make ‘good trouble, necessary trouble.'"
Elizabeth Warren: Lewis was "the moral compass of our nation"
US Sen. Elizabeth Warren has called John Lewis a "true American hero" and "the moral compass of our nation" following the civil rights icon's death.
"May his courage and conviction live on in all of us as we continue to make good trouble for justice and opportunity," she added. "Rest in power, John."
Barack Obama: Lewis "will continue, even in his passing, to serve as a beacon"
Former President Barack Obama said John Lewis will "continue, even in his passing, to serve as a beacon" in America's journey towards a more perfect union.
"He loved this country so much that he risked his life and his blood so that it might live up to its promise. And through the decades, he not only gave all of himself to the cause of freedom and justice, but inspired generations that followed to try to live up to his example," he said in a statement following Lewis' passing.
"Not many of us get to live to see our own legacy play out in such a meaningful, remarkable way. John Lewis did. And thanks to him, we now all have our marching orders – to keep believing in the possibility of remaking this country we love until it lives up to its full promise."
Mitch McConnell: "Our nation will never forget this American hero"
Republican Senate Majority Leader Mitch McConnell has called John Lewis a "pioneering civil rights leader," saying the 80-year-old put his life on the line to "fight racism, promote equal rights, and bring our nation in to greater alignment with its founding principles."
In a statement mourning Lewis' death, McConnell recalled joining hands as members of Congress and singing "We Shall Overcome" at a 2008 ceremony honoring civil rights leader Martin Luther King Jr.
"It could not have been more humbling to consider what he had suffered and sacrificed so those words could be sung in that place," he said.
"Dr. King famously said 'the arc of the moral universe is long, but it bends towards justice.' but progress is not automatic. Our great nation's history has only bent towards justice because great men like John Lewis took it upon themselves to help bend it. Our nation will never forget this American hero."