BIRMINGHAM, Ala — On this day 56-years-ago, four young black girls were murdered when a bomb planted by Ku Klux Klan members exploded at their 16th Street Baptist Church in Birmingham, Alabama. 

Their names were Addie Mae Collins, 14, Denise McNair, 11, Carole Robertson, 14,  and Cynthia Wesley, 14. 

Some 400 people were inside the church at the time of the bombing, and 17 other church-goers were injured in the blast. Riots broke out in Birmingham as racial tensions simmered to a new high and two other young black boys, Virgil Ware, 13, and Johnny Robinson, 16, were shot to death by white men. 

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FILE - In this Sept. 15, 1963 file photo, damaged automobiles show the force generated by an explosion which tore large pieces of stone from the 16th Street Baptist Church during services in Birmingham, Ala. A bomb planted by Ku Klux Klansmen ripped apart the building and killed four black girls. (AP Photo)
AP

Ware was gunned down by a white teenager and Robinson was shot to death by a police officer who fired at a crowd of young black boys. 

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The 16th Street Baptist Church was a predominantly black congregation which also served as a meeting place for prominent civil rights leaders. The Ku Klux Klan attacked the church just two and a half weeks after Dr. Martin Luther King Jr. led the civil rights March on Washington.

Outrage over the girls' death and the protests which followed helped draw national attention to the civil rights movement. It also paved the way for the passage of the 1964 Civil Rights Act and abolished Jim Crow laws that upheld segregation across the South.

Explosive Devices History of Violence
FILE - In this Sept. 15, 1963, file photo, firefighters and ambulance attendants remove a covered body from the 16th Street Baptist Church in Birmingham, Ala., after by a deadly explosion detonated by members of the Ku Klux Klan during services. The 2018 mail-bomb scare has reopened old wounds for Lisa McNair, whose life has been shaped by the blast that occurred a year before she was born, killing her sister, Denise, 11. "It's like, 'Ugh, again.' When are we going to get this right?" asked McNair. "It's been 55 years since Denise was killed. Why do we keep going there in America? Why do we keep going there as a world and human beings?" (AP Photo)
AP

Decades after the attack, four Klansmen were eventually convicted for their roles in what's now considered one of the single most horrifying acts committed by racists during the civil rights era. 

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One of the perpetrators, Thomas Edwin Blanton Jr. is still alive in jail. He is now 89-years-old and was denied parole in 2016. 

Democratic presidential candidate Joe Biden visited the church on Sunday, and said the country hasn't "relegated racism and white supremacy to the pages of history" as he framed current tensions in the context of the movement's historic struggle for equality.

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And, taking to social media, many still remember and acknowledge the girls' deaths as a defining moment in the historical civil right moments.

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