 King considered their struggle to be a vital part of the Poor People's Campaign he was planning.A day after delivering his stirring "I've Been to the Mountaintop" sermon, which has become famous for his vision of American society, King was assassinated on April 4, 1968.Riots broke out in black neighborhoods in more than 110 cities across the United States in the days that followed, notably in Chicago, Baltimore, and Washington, D.C.