Her group stayed inside a church until it was time to march, and she worried that few people would show.
"We thought, 'Oh, it's going to fail,'" Johnson remembers. "Then, of course, when we came out and started marching, there were all of these people coming from every corner of the country."
Johnson, a Democratic delegate from Minnesota, is among at least a half-dozen witnesses to King's speech who will be on hand Thursday in Denver to see Barack Obama accept his party's nomination for president, a huge milestone in the fulfillment of the dream that King sketched out so long ago.
And while those who attended what was called the March on Washington for Jobs and Freedom have seen progress for blacks through the years, Obama's journey from community organizer to U.S. senator to the top of his party's presidential ticket was something they hadn't envisioned - at least not so soon.
It is a coincidence that Obama is accepting his party's nomination on the 45th anniversary King's speech, but one that Democrats have been happy to embrace. Convention officials have made a point of highlighting the anniversary and scheduled a special breakfast Thursday to mark the occasion.
Obama was 2-years-old when doctor king shared his dream. At the 2004 Democratic National Convention, Obama burst onto the national scene with a speech that paid homage to King and those who came before him.
"I stand here knowing that my story is part of the larger American story, that I owe a debt to all of those who came before me, and that, in no other country on earth, is my story even possible."
The nomination of a black man for president is something "I never thought I would live to see," said Henry L. Marsh III, 74, a state senator from Richmond, Va. He was there in Washington for King's speech, and will be on hand for Obama's nomination acceptance speech at Invesco Field at Mile High stadium.
Marsh remembers being mesmerized by all of the speakers that day in 1963, but he said King's speech was the "icing on the cake." Standing on the steps of the Lincoln Memorial, King spoke of his dream that one day the descendants of former slaves and former slave owners "will be able to sit down together at the table of brotherhood" and that his children would "live in a nation where they will not be judged by the color of their skin but by the content of their character."
The speech "gave me a different perspective of the struggle I was in," said Marsh, who had been working as a lawyer in Virginia to desegregate courtrooms. "It made me realize that I was part of something much bigger than what I thought before."
While Marsh thinks some of the struggles King talked about continue today, he's proud of how far he and other blacks have come. He remembers sitting on the black side of the courtroom in the early '60s; now he's chairman of the legislative committee that selects judges in Virginia.
"The American system makes an Obama possible," Marsh said.
Lucy Buckner-Watson, a delegate from Inver Grove Heights, Minn., and Barbara Lee, a delegate from Staunton, Va., were teenagers when they marched and heard King's "Dream" speech.
Lee, 60, was the youngest member of a group from Staunton who made the trip on an old bus. "There was a hole in the bus floor and there was a piece of cardboard on the floor that kept flapping up as we rode," she said. "It was a long trip."
Lee remembers the crowd becoming quiet just before King spoke. "When he said that someday we'll all be one, it just stuck in my mind," said Lee, a longtime member of the National Association for the Advancement of Colored People.
From the first time she saw Obama speak, Lee said, she could tell he carried a similar message.
She has a button that says "A Legacy of Hope" with pictures of both King and Obama, and wouldn't miss Obama's acceptance speech for anything.
"This is the most important thing that I've done in my entire life," said Lee, who, like most delegates, paid her own way to Denver. "I'm on Social Security, but I just thought, 'I'm going, even if it takes me 10 years to pay it back.'"
"When we leave there we are going to have to keep that energy going. We've got to," said Buckner-Watson, 63. She hopes her 86-year-old father, who has terminal cancer, will live long enough to see Obama win.
"I want him to be aware and to be here on this side of heaven and realize a black man being president. Because he shared with us that he had seen a black man hung," Buckner-Watson said.
"I am so very, very proud of my people," she said. "Although I know a lot have suffered way more than we have, it's like having some kind of arriving."
For a transcript of Dr. King's 1963 "I Have a Dream" speech click here.