If the legendary gospel vocalist Mahalia Jackson had been somewhere other than the National Mall in Washington, D.C., on August 28, 1963, her place in history would still have been assured purely on the basis of her musical legacy. But it is almost impossible to imagine Mahalia Jackson having been anywhere other than center stage at the historic March on Washington on August 28, 1963, where she not only performed as the lead-in to Dr. Martin Luther King, Jr. and his “I Have a Dream” speech, but she also played a direct role in turning that speech into one of the most memorable and meaningful in American history.

By 1956, Mahalia Jackson (1911-1972) was already internationally famous as the Queen of Gospel when she was invited by the Reverend Ralph Abernathy, director of the Southern Christian Leadership Conference (SCLC), to appear in Montgomery, Alabama, in support of the now-famous bus boycott that launched the modern civil rights movement and made Rosa Parks a household name. It was in Alabama that Jackson first met and befriended the Reverend Dr. Martin Luther King, Jr., whom she would support throughout his career.

Indeed, if Martin Luther King, Jr., had a favorite opening act, it was Mahalia Jackson, who performed by his side many times. On August 28, 1963, as she took to the podium before an audience of 250,000 to give the last musical performance before Dr. King’s speech, Dr. King himself requested that she sing the gospel classic “I’ve Been ‘Buked, and I’ve Been Scorned.” Jackson was just as familiar with Dr. King’s repertoire as he was with hers, and just as King felt comfortable telling her what to sing as the lead-in to what would prove to be the most famous speech of his life, Jackson felt comfortable telling him in what direction to take that speech.

The story that has been told since that day has Mahalia Jackson intervening at a critical junction when she decided King’s speech needed a course-correction. Recalling a theme she had heard him use in earlier speeches, Jackson said out loud to Martin Luther King, Jr., from behind the podium on the steps of the Lincoln Memorial, “Tell them about the dream, Martin.” And at that moment, as can be seen in films of the speech, Dr. King leaves his prepared notes behind to improvise the entire next section of his speech—the historic section that famously begins “And so even though we face the difficulties of today and tomorrow, I still have a dream. It is a dream deeply rooted in the American dream….”

READ MORE: The March on Washington