Martin Luther King stood on the steps in front of the Lincoln Memorial and delivered his stirring I Have a Dream speech on August 28, 1963. The date was the 100 year anniversary of Lincoln’s signing of the Emancipation Proclamation in the midst of the Civil War.
The speech is just 17 minutes long.
Clear high quality audio of the entire speech is here, courtesy of American Rhetoric.
Unfortunately the best quality video is restricted by holders of the MLK copywrite. However, a very good video is available here, courtesy of YouTube.