Written By: Eliza Berman

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 movement would fare in the absence of its most outspoken leader, still resonate today as a new chapter in American civil rights 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 edited this gallery for LIFE.com. Follow her on Twitter @lizabethronk.

American Civil Rights leader Reverend Martin Luther King Jr. stands in front of a bus at the end of the Montgomery bus boycott, Montgomery, Alabama, December 26, 1956.

Reverend Martin Luther King, Jr. stands in front of a bus at the end of the Montgomery bus boycott, Montgomery, Alabama, Dec. 26, 1956.

Don Cravens / The LIFE Images Collection

Civil rights leader Rev. Martin Luther King speaking from pulpit at mass meeting about principles of non-violence before leading assembly to ride newly integrated busses after successful boycott.

Rev. Martin Luther King speaking from pulpit at mass meeting about principles of non-violence before leading an assembly to ride newly integrated busses after successful boycott.

Don Cravens / The LIFE Images Collection

Rev. Martin Luther King Jr. speaking at 'Prayer Pilgrimage for Freedom' at Lincoln Memorial, 1957.

Rev. Martin Luther King Jr. speaking at ‘Prayer Pilgrimage for Freedom’ at Lincoln Memorial, 1957.

Paul Schutzer / The LIFE Picture Collection

Martin Luther King Jr. Trial, Montgomery Alabama Integration, 1958.

Martin Luther King, Jr. in Montgomery Alabama, 1958.

Grey Villet / The LIFE Picture Collection

Martin Luther King Jr. holding his son Martin III as his daughter Bernice and wife Coretta greet him at the airport upon his release from Georgia State prison after incarceration for leading boycotts, 1960.

Martin Luther King Jr. holds his son Martin III as his daughter Bernice and wife Coretta greet him at the airport upon his release from Georgia State prison after his incarceration for leading boycotts, 1960.

Donald Uhrbrock / The LIFE Images Collection

Rev. Martin Luther King Jr. (C) speaking with Rev. Ralph Abernathy (2nd R) and others, 1961.

Martin Luther King Jr. (center) speaks with Rev. Ralph Abernathy (2nd from right) and others, 1961.

Paul Schutzer / The LIFE Picture Collection

Reverend Martin Luther King Jr. addressing rally in Detroit, 1963.

Reverend Martin Luther King Jr. addressing rally in Detroit, 1963.

Francis Miller / The LIFE Picture Collection

Leaders of March on Washington for Jobs and Freedom marching w. signs (R-L): Matthew Ahmann, Floyd McKissick, Martin Luther King Jr., Rev. Eugene Carson Blake and unidentified.

Leaders of the March on Washington for Jobs and Freedom march with signs (from R-L): Matthew Ahmann, Floyd McKissick, Martin Luther King Jr., Rev. Eugene Carson Blake and an unidentified man.

Robert W. Kelley / The LIFE Picture Collection

Civil rights leader Dr. Martin Luther King Jr.speaking with President Lyndon Johnson during a visit to the White House, 1963.

Martin Luther King, Jr. speaks with President Lyndon B. Johnson during a visit to the White House, 1963.

Stan Wayman / The LIFE Picture Collection

Civil Rights leader Martin Luther King Jr leads a prayer in a church before the second Selma to Montgomery Civil Rights march, also known as 'Turnaround Tuesday', Selma, Alabama, 9th March 1965.

Martin Luther King, Jr leads a prayer in a church before the second Selma to Montgomery Civil Rights march, also known as ‘Turnaround Tuesday’, Selma, Ala., March 1965.

Frank Dandridge / The LIFE Images Collection

Civil rights leaders Floyd B. McKissick (fore, 3L), Dr. Martin Luther King Jr. (4R) and Stokely Carmichael (2R) participating in voter registration march after originator James H. Meredith was shot, 1966.

Floyd B. McKissick, Martin Luther King, Jr. and Stokely Carmichael participate in a voter registration march after its organizer, James H. Meredith, was shot and wounded, 1966.

Lynn Pelham / The LIFE Picture Collection

Civil rights leader Dr. Martin Luther King Jr. sitting with demonstrators who walked through Mississippi to encourage voter registration., 1966.

Martin Luther King, Jr. sits with demonstrators who walked through Mississippi to encourage voter registration, 1966.

Vernon Merritt III / The LIFE Images Collection

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