"I Have A Dream" by Martin Luther King, August 28, 1963.
This is the famed speech whose final cry, “Free at last, free at least, God almighty we are free at last!” secured the Civil Rights movements national recognition in the United States. (From US Constitution.net) “King helped organize a massive march on Washington, DC, on August 28, 1963...King's appearance was the last of the event; the closing speech was carried live on major television networks. On the steps of the Lincoln Memorial, King evoked the name of Lincoln in his "I Have a Dream" speech, which is credited with mobilizing supporters of desegregation and prompted the 1964 Civil Rights Act. The next year, King was awarded the Nobel Peace Prize.”