When Martin Luther King, Jr. was assassinated in April 1968, LIFE magazine remembered him for his "exalted dream of freedom," one he "died in Memphis for daring to have." The editors' words, wondering aloud how the civil-rights movement would fare in the absence of its most outspoken leader, still resonate today as a new chapter in American race relations continues to unfold:
King was a thoroughly good man who achieved greatness by showing forth the Negro cause at its best. His was the old American cause of equal rights for all men, and King put it in the form in which this generation of Americans must face it. His death may hinder or help that cause; perhaps both. But all of us owe him the honor of not letting ourselves distort, becloud or belittle the cause he brought to such noble purity of expression.
In honor of Martin Luther King, Jr. Day, and the anniversary of King's birth on Jan. 15, 1929, here are some of the most powerful images of King made by LIFE's photographers.
Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter @lizabethronk.