The Rev. Al Sharpton, Martin Luther King III, the Rev. Jesse Jackson, comedian Dick Gregory and actors Jamie Foxx and Chris Tucker were among those who attended Sunday's event.
Foxx told a crowd that packed the memorial that this is a "spectacular time" for African-Americans.
Sharpton called the weekend an "intersection of history," with the nation's first black president taking the oath of office for a second term the same weekend as the federal holiday commemorating King's life. Sharpton says there was a time when no one believed the country would have either a black president or a federal holiday for a black civil rights leader.