In 1963, when Charles McDew stepped down as chairman of the Student Nonviolent Coordinating Committee (SNCC), Lewis, one of the founding members of SNCC, was elected to take over.
 Lewis's experience at that point was already widely respected.
His courage and tenacious adherence to the philosophy of reconciliation and nonviolence made him emerge as a leader.
By this time, he had been arrested 24 times in the nonviolent movement for equal justice.
He served as chairman until 1966.
During his tenure, SNCC opened Freedom Schools, launched the Mississippi Freedom Summer, and organized some of the voter registration efforts during the 1965 Selma voting rights campaign.
As the chairman of SNCC, Lewis had written a speech in reaction to the 1963 Civil Rights Bill.
The planned speech denounced the bill because it did not protect African Americans against police brutality or provide African Americans with the right to vote; it  described it as "too little and too late."
But when copies of the speech were distributed on August 27, other chairs of the march insisted that it be revised.
James Forman re-wrote Lewis's speech on a portable typewriter in a small anteroom behind Lincoln's statue during the program.
SNCC's initial assertion "we cannot support, wholeheartedly the [Kennedy] civil rights bill” was replaced with “We support it with great reservations."

In 1963, as chairman of SNCC, Lewis was named one of the "Big Six" leaders who were organizing the March on Washington, the occasion of Dr. Martin Luther King's celebrated "I Have a Dream" speech, along with Whitney Young, A. Philip Randolph, James Farmer, and Roy Wilkins.
Discussing the occasion, historian Howard Zinn wrote: "At the great Washington March of 1963, the chairman of the Student Nonviolent Coordinating Committee (SNCC), John Lewis, speaking to the same enormous crowd that heard King's "I Have a Dream" speech, was prepared to ask the right question: 'Which side is the federal government on?'
That sentence was eliminated from his speech by the other organizers of the March to avoid offending the Kennedy Administration.
Lewis and his fellow SNCC workers had experienced the federal government's passivity in the face of Southern violence; Lewis, the youngest speaker that day, begrudgingly acquiesced and delivered the edited speech as the fourth speaker that day, ahead of the "I Have a Dream" speech by King who served as the final speaker that day.

In 1964, Lewis coordinated SNCC's efforts for Freedom Summer, a campaign to register black voters across the South and expose college students from around the country to the perils of African-American life in the South.
Lewis traveled the country, encouraging students to spend their summer break trying to help people vote in Mississippi, the most recalcitrant state in the union.
Lewis became nationally known during his prominent role in the Selma to Montgomery marches when, on March 7, 1965 – a day that would become known as "Bloody Sunday" – Lewis and fellow activist Hosea Williams led over 600 marchers across the Edmund Pettus Bridge in Selma, Alabama.
At the end of the bridge, they were met by Alabama State Troopers who ordered them to disperse.
When the marchers stopped to pray, the police discharged tear gas and mounted troopers charged the demonstrators, beating them with nightsticks.
Lewis's skull was fractured, but he escaped across the bridge to Brown Chapel, a church in Selma that served as the movement's headquarters.
Lewis bore scars on his head from the incident for the rest of his life.
In 1963, when Charles McDew stepped down as chairman of the Student Nonviolent Coordinating Committee (SNCC), Lewis, one of the founding members of SNCC, was elected to take over.  Lewis's experience at that point was already widely respected. His courage and tenacious adherence to the philosophy of reconciliation and nonviolence made him emerge as a leader. By this time, he had been arrested 24 times in the nonviolent movement for equal justice. He served as chairman until 1966. During his tenure, SNCC opened Freedom Schools, launched the Mississippi Freedom Summer, and organized some of the voter registration efforts during the 1965 Selma voting rights campaign. As the chairman of SNCC, Lewis had written a speech in reaction to the 1963 Civil Rights Bill. The planned speech denounced the bill because it did not protect African Americans against police brutality or provide African Americans with the right to vote; it  described it as "too little and too late." But when copies of the speech were distributed on August 27, other chairs of the march insisted that it be revised. James Forman re-wrote Lewis's speech on a portable typewriter in a small anteroom behind Lincoln's statue during the program. SNCC's initial assertion "we cannot support, wholeheartedly the [Kennedy] civil rights bill” was replaced with “We support it with great reservations."
In 1963, as chairman of SNCC, Lewis was named one of the "Big Six" leaders who were organizing the March on Washington, the occasion of Dr. Martin Luther King's celebrated "I Have a Dream" speech, along with Whitney Young, A. Philip Randolph, James Farmer, and Roy Wilkins. Discussing the occasion, historian Howard Zinn wrote: "At the great Washington March of 1963, the chairman of the Student Nonviolent Coordinating Committee (SNCC), John Lewis, speaking to the same enormous crowd that heard King's "I Have a Dream" speech, was prepared to ask the right question: 'Which side is the federal government on?' That sentence was eliminated from his speech by the other organizers of the March to avoid offending the Kennedy Administration. Lewis and his fellow SNCC workers had experienced the federal government's passivity in the face of Southern violence; Lewis, the youngest speaker that day, begrudgingly acquiesced and delivered the edited speech as the fourth speaker that day, ahead of the "I Have a Dream" speech by King who served as the final speaker that day.
In 1964, Lewis coordinated SNCC's efforts for Freedom Summer, a campaign to register black voters across the South and expose college students from around the country to the perils of African-American life in the South. Lewis traveled the country, encouraging students to spend their summer break trying to help people vote in Mississippi, the most recalcitrant state in the union. Lewis became nationally known during his prominent role in the Selma to Montgomery marches when, on March 7, 1965 – a day that would become known as "Bloody Sunday" – Lewis and fellow activist Hosea Williams led over 600 marchers across the Edmund Pettus Bridge in Selma, Alabama. At the end of the bridge, they were met by Alabama State Troopers who ordered them to disperse. When the marchers stopped to pray, the police discharged tear gas and mounted troopers charged the demonstrators, beating them with nightsticks. Lewis's skull was fractured, but he escaped across the bridge to Brown Chapel, a church in Selma that served as the movement's headquarters. Lewis bore scars on his head from the incident for the rest of his life.
John Lewis