Today in 1963, Martin Luther King, Jr. delivered his 17-minute “I Have a Dream” speech.

Delivered to over 250,000 civil rights supporters from the steps of the Lincoln Memorial during the March on Washington, Martin Luther King, Jr.’s “I Have A Dream” speech was a defining moment of the American Civil Rights Movement.

The speech was drafted with the assistance of Stanley Levison and Clarence Benjamin Jones in Riverdale, New York City. Jones has said that “the logistical preparations for the march were so burdensome that the speech was not a priority for us” and that, “on the evening of Tuesday, Aug. 27, [12 hours before the March] Martin still didn’t know what he was going to say”.

King was the sixteenth out of eighteen people to speak that day, according to the official program.

Beginning with a reference to the Emancipation Proclamation, which freed millions of slaves in 1863, King observes that: “one hundred years later, the Negro still is not free”. Toward the end of the speech, King departed from his prepared text for a partly improvised peroration on the theme “I have a dream”, prompted by Mahalia Jackson’s cry: “Tell them about the dream, Martin!” In this part of the speech, which most excited the listeners and has now become its most famous, King described his dreams of freedom and equality arising from a land of slavery and hatred.

The Federal Bureau of Investigation noticed the speech’s popularity, which provoked them to expand their COINTELPRO operation against the SCLC, and to target King specifically as a major enemy of the United States.

The speech was ranked the top American speech of the 20th century in a 1999 poll of scholars of public address.