They've been talking about unity and about equality, as the three leading Democratic presidential candidates remember Martin Luther King on the holiday in his honor.
Barack Obama, John Edwards and Hillary Rodham Clinton were all at the Statehouse in Columbia, South Carolina, to talk to the hundreds gathered at a rally.
Obama talked about the need for unity. He says the nation must work to remove what he called barriers to justice and equality.
Edwards says the presence of a black man and a woman among the leading candidates speaks to the progress the nation has made since King led the civil rights movement. But he says much remains to be done.
Clinton says those of King's era laid an important foundation for improvement. But she says the stakes are high in this year's election to continue the progress.