He was a key figure in the US civil rights movement, often mentioned in the same breath as the likes of Martin Luther King Jr.
Flags in Atlanta have been lowered to half-mast “indefinitely” following the death of John Lewis, aged 80.
The Democratic Congressman was the youngest and last survivor of Big Six civil rights leaders who helped galvanise opposition to racial segregation in the US.
He was best known for leading some 600 protesters in the Bloody Sunday march across the Edmund Pettus Bridge in Selma.
At age 25 — walking at the head of the march with his hands tucked in the pockets of his tan overcoat — Mr Lewis was knocked to the ground and beaten by police.
His skull was fractured, and nationally televised images of the brutality forced the country’s attention on racial oppression in the South.
Within days, Reverend King led more marches in the state, and President Lyndon Johnson soon was pressing Congress to pass the Voting Rights Act.
The bill became law later that year, removing barriers that had barred black people from voting.
Mr Lewis turned to politics in 1981, when he was elected to the Atlanta City Council, then won his seat in Congress in 1986.
Mr Lewis was made the party’s senior deputy whip in 2006, a behind-the-scenes leadership post in which he helped keep the party unified.
Mr Lewis said he had been arrested 40 times in the 1960s, five more as a congressman.
Atlanta mayor Keisha Lance Bottoms said words cannot describe the loss.
She added: “The people of Atlanta often called upon Congressman Lewis for counsel, guidance, and assistance with getting into good trouble.
“No matter how busy his schedule, or important his Washington duties were, he answered.”
Arthur Blank, the owner of the NFL’s Atlanta Falcons, said the city lost two civil rights icons in a single day in Mr Lewis and the Reverend CT Vivian, an early and important adviser to Martin Luther King Jr.
Rev Vivian died on Friday at the age of 95, and Mr Lewis died hours later.
Mr Blank said: “John risked his life to end legalised racial segregation and make America a better place for us and future generations.
“That’s the enduring legacy of one of the most courageous people I ever met.”
US President Donald Trump ordered flags at half-mast at the White House and all federal public buildings and grounds, including embassies abroad and all military posts and naval stations, throughout the day on Saturday.
In a tweet, Mr Trump said: “Saddened to hear the news of civil rights hero John Lewis passing.
“Melania and I send our prayers to he and his family.”
Mr Lewis’s wife of four decades, Lillian Miles, died in 2012. They had one son, John Miles Lewis.