"nightline" with cynthia mcfadden. >>> good evening, when martin luther king jr. stood up to address the nation on the steps of the lincoln memorial, his words did not use the phrase "i have a dream." he had used those words before, but they wanted something different. and then, mahalia jackson said "tell them about the dream." and he said the words that still resonate today. two young african american girls went to the gathering, and had a message. today, they talk about what has changed and what has not. >> ♪ ♪ >> with songs and symbols from the struggle, a new generation of the faithful. >> and we thank the mighty god for giving us a martin luther