As we celebrate Dr. Martin Luther King, Jr. Day today, many Americans know this American hero as a champion of racial equality. But few know that he spent the last years of his life fighting for an end to the Vietnam War and a less militaristic foreign policy, or that he championed economic justice as well.

King spent the last days of his life working for justice for union workers in Memphis, Tennessee.

On April 3, 1968, King traveled there, where he delivered his famous ai???Iai??i??ve Been To The Mountaintopai??? speech, during which he endorsed a ai???human rights revolutionai??? based around eradicating racism, poverty, and militarism.

King had arrived in Memphis to support a strike by the cityai??i??s sanitation workers,Ai??who struckAi??to gain collective bargaining rights and better conditions following the deaths of two city workers in an accident. King called upon the city to respect the ai???dignity of labor,ai??? saying that all workers deserved fair treatment. He also said it was a crime for a rich country like the United States to pay some people starvation wages. Documentary footage from the AFSCME union captured Kingai??i??s address to the workers:

King implored people to think about a new kind of “unselfishness” in his last public speech, and asked people to support workers like the sanitation employees on strike:

That’s the question before you tonight. Not, “If I stop to help the sanitation workers, what will happen to all of the hours that I usually spend in my office every day and every week as a pastor?” The question is not, “If I stop to help this man in need, what will happen to me?” “If I do not stop to help the sanitation workers, what will happen to them?” That’s the question.

Dr. King was assassinated one day after he gave this powerful speech.