Nearly 50 years after the March on Washington, the sole surviving speaker from that day, Democratic Rep. John Lewis of Georgia, spoke with ABC's Byron Pitts about the pivotal event, recalling the moment he knew the day would live forever in American history.

"When I…stepped to the podium I saw hundreds and hundreds of young people," Lewis recalled during an interview for "This Week."

"And I said to myself, 'this is it,'" he remembered.

On that day in 1963 when Martin Luther King Jr. delivered his famous "I Have a Dream," speech, Lewis described himself as an "old soul" even at the age of 23, having been engaged in the fight for equal rights for African Americans.

50 Years Later: What Would You March For? #IMarchFor

"When you have been sitting on a lunch counter stool and someone walk up and spit on you, or pour hot water or hot coffee on you…and you said you're committed to non violence…you have to grow up. Or to go on the freedom rides in 1961, the same year that President Barack Obama was born, and to be beaten…you had to grow up," Lewis said.

"So by the time of the March on Washington, I was 23, but I was an older person," he said.

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Lewis was joined in Washington, D.C. by some 250,000 people on August 28, 1963 including then 12-year-old Edith Lee Payne, who had traveled for more than nine hours by bus with her mother to be on the National Mall that day.

"I held on to every word that he said - just like everyone else that was there," she told Pitts.

Former Ambassador Andrew Young, who was a top aide to King at the time, told Pitts he wasn't initially going to attend the March, until he received a call from King. Young - and others in King's inner circle - initially thought the movement should focus its attention on recent bombings in Birmingham, Ala. The March was organized by King and five other civil rights leaders.

"We felt that this was a picnic on the park. And that the real action was in the South," Young said.

"I was going to watch it on television. And Dr. King called a couple of days ahead and said 'you and Jean get on a plane and come on up here,'" he said.

Young told Pitts that King was "not at all" nervous about his delivering his planned remarks, which he did, in less than nine minutes. But then King continued, going on to deliver the most memorable portion of his speech - the portion about his dream.

March on Washington: 'Their March Is Now Our March'

"The spirit told him to lay down that paper and just go for it," Lewis said.

Lewis, who still visits the Lincoln Memorial to "reflect" and "remember" recalled what was at stake that day in 1963.

"The future of America as one nation, as one people was at stake. We could've gone in a different direction," Lewis said.

"He helped hold us together," he said.

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