Wednesday, Aug. 28, the day of the march, arrived at the end of a long sweltering summer of racial discord, and Washington was frightened that maybe it was next.
The government ordered bars and liquor stores closed. Major League Baseball was canceled. The National Guard was put on alert. The White House had prepared an executive order for martial law.
An army of citizens was descending on the nation's Capitol.
Veteran newsman Roger Mudd recalls, "Washington had never had a march like this. They didn't know what to expect. They expected the worst. They had seen on television the violence, the dogs, the hoses. They hoped it wouldn't happen in Washington, but they didn't know."
Under the careful direction of the march's chief planner, Bayard Rustin, hundreds of special buses and trains and carpools were now delivering thousands and thousands of people to Washington.
A group of teenagers had walked the 225 miles from New York. A young man named Ledger Smith roller skated from Chicago. By 10 a.m. more than 40,000 people had arrived.
The night before, King was still struggling to finish his speech.
Young said, "He went over it and over it and he crossed out words three-four times, trying to get not only the right word and meaning, but the right rhythm and the right sound."
The Rev. Walter Fauntroy remembers, "He knew all the lines that got the best response, and our problem was which of the lines we needed to put in the speech, because it's not just 3,000 people in a church now, or 5 or 10,000 people in a stadium. This was the world stage."
There were several drafts of the speech, and from the very first, King included what would be a key reference: he said the marchers had come to the nation's capital to "cash a check."
King made the point that the nation's founders had signed a promissory note to which all Americans would become heir. He was at the helm of a movement that said America had written black Americans a bad check.
"It was in the face of this terrible injustice that he believed that America could live out the true meaning of her creeds. And so this was a fulfillment of the promise of Washington and Jefferson and John Adams."
At 11 a.m. the crowds around the Washington monument spontaneously set off for the Lincoln Memorial. The march's leaders had to rush to catch up halfway down Constitution Avenue. All three television networks were going on the air.
By noon there were a quarter of a million people on the Washington Mall.
The program got under way at about two o'clock. One of those who entertained was the young folk singer Joan Baez. Harry Belafonte organized a celebrity contingent that included Paul Newman, James Garner, Marlon Brando, Sidney Poitier, and Charlton Heston.
Hedrick Smith remembers, "It was so peaceful. It was like a state fair, it was like a festival. It was so ebullient and non-threatening that it was surprising. It was surprising almost in its ordinariness … it was not just a protest, it was a celebration."
Behind the scenes, a small group of justice department lawyers was working to make sure the march went smoothly. Plainclothes police were brought in from New York.
The Kennedy Administration worked with the labor unions to make sure there were plenty of white faces in the crowd.