You're probably pretty familiar with some part of Martin Luther King Jr's "I Have a Dream" Speech. You can probably easily compel your mind to hear Dr. King's voice talking about the "red hills of Georgia," before concluding with "the words of the old Negro spiritual, 'Free at last! Free at last! Thank God Almighty, we're free at last!" And you're likely to hear bits of it again in these days leading up to the 50th anniversary of the March on Washington.
But those are a few seconds of a more than 15-minute long speech, during which King talked not only about racial justice, but specifically addressed "the unspeakable horrors of police brutality" wreaked upon blacks, twice. As The Atlantic points out, however, you're not likely to have watched the brilliant speech in its entirety due to complicated and ever-evolving copyright laws.
At least one site has posted the speech in its entirety, however, as "a small act of civil disobedience."