Martin Luther King's most famous speech, which called for an end to racism in the United States, is frequently called the "I Have a Dream" speech. King delivered the speech on August 28, 1963, in Washington, D.C.
King's iconic speech was delivered in front of 250,000 people during the March on Washington in 1963. He had been using "dream" language as a recurrent theme in his speeches since 1960. "I Have a Dream" was written with the assistance of his advisers and friends, Stanley Levison and Clarence B. Jones.
Jones has commented that they were so busy with the march that the speech was prepared less than 12 hours before King was to speak. The full text of the speech is available at Nobelprize.org.