It was only a few weeks ago when the nation commemorated the 50th anniversary of the March on Washington for Jobs and Freedom. It was an opportunity to look at the progress of African-Americans over the past five decades and a reminder that the fight for social justice, civil rights, and human rights is a constant battle.

Before addressing the crowd, President Obama joined the King family—Martin III, Dexter, and Bernice—in ringing a bell that once hung in the 16th Street Baptist Church in Birmingham, Alabama. Less than a month after Martin Luther King Jr. made his historic “I Have a Dream” speech, the church was bombed, killing four black girls: Denise McNair, 11; Carole Robertson, 14; Cynthia Wesley, 14, and Addie Mae Collins, 14.

The 16th Street church was the first and largest black church in Birmingham. Located in the heart of downtown, it was known to host such historic figures as Thurgood Marshall, W.E.B. DuBois, and, later, Hillary Clinton, as well as a junior senator from Illinois who would later become America’s first black president. During the 1960s, 16th Street was the hub of the city’s civil-rights activities. There, civil-rights activists strategized, held mass meetings, sponsored rallies, and planned demonstrations in the fight against segregation.

At the height of the civil-rights movement, Birmingham was known as Bombingham. By the fall of 1963, there had been more than 80 unsolved bombings in the city, including at the home of A.D King, Martin Luther King Jr.’s brother.

But September 15, 1963, would go down in history as a day like no other. A bomb planted in the church’s basement exploded, killing the four girls and injuring many others. It was “a moment that the world would never forget,” Lonnie Bunch told The Washington Post. Bunch is the director of the Smithsonian’s National Museum of African American History and Culture. Shard glass from the historic church was recently donated to the museum, which is scheduled to open in 2015.

For the first 14 years after the bombing, no one was arrested. Robert Chambliss was eventually convicted of the crime in 1977. And three decades after that horrific explosion, Thomas Blanton Jr. and Bobby Frank Cherry were convicted of murder and sentenced to life in prison. It would be the only bombing solved in Birmingham.

Earlier this year President Obama signed a bill giving the Congressional Gold Medal to the victims of the bombing. On September 10, the families of the four girls gathered in Washington, D.C., for a bipartisan ceremony at the U.S. Capitol. The medal will be housed at the Birmingham Civil Rights Institute, across the street from the 16th Street Baptist Church.

Carolyn McKinstry was the 15-year-old Sunday-school secretary of 16th Street Baptist Church when it was bombed 50 years ago and was friends with the four girls who died during the explosion. Terrorism was a way of life for children growing up in segregated Birmingham, said McKinstry, who documented that time in her book, While the World Watched: A Birmingham Bombing Survivor Comes of Age During the Civil Rights Movement. She talks about that tragic day and the impact the death of four little girls had on the civil-rights movement.

Lottie L. Joiner: Take me back to that day 50 years ago, September 15, 1963.

Carolyn McKinstry: At the end of Sunday school, I would get up and make a report. Around 10:15 a.m. I got up to collect the reports. I started upstairs. You had to pass the girls’ bathroom. I paused at the doorway, because they [Addie Mae, Carol, Cynthia, Denise] were all standing there, combing their hair, playing, and talking. We were all good friends, and we were excited about two things that Sunday. It was Youth Sunday, and that meant we got to do everything. We were the choir. We were the ushers, the speakers. The second thing was, after church we were going to have a gathering with punch and dancing. I knew my report had to be done at a certain time, so I went on up the stairs. When I got to the office, the phone was ringing. The caller on the other end of the phone said, “Three minutes.” Male caller. But he hung up just as quickly as he said that. I stepped out into the sanctuary to get more reports, and I only took about 15 steps into the sanctuary, and the bomb exploded.

What did you do?

When the bomb exploded, it felt like the building shook. Everything came crashing in, the glass and the windows in the church. I fell on the floor because someone said, “Hit the floor.” We were all on the floor for just a couple of seconds. And then I could hear people getting up and running out. I got up, and I went outside. I was looking for my two little brothers. One of the first things we noticed was that the church was already surrounded by policemen. People were in panic mode. They were everywhere looking for their family members.

How did you learn that the four young ladies died?

When I went home that Sunday, I remember one or two people calling my mother, looking for their children. One of them was Mrs. Robertson, Carole’s mother. Later somebody else called and said that the girls in the bathroom never made it out. My heart jumped. I knew who they were talking about. I was shocked. I was numb. The bomb exploded on Sunday at 10:22 a.m. On Monday morning at 8 o’clock, I was sitting in my classroom. No one said anything. No one said, “Let’s have a moment of silent prayer.” No one said, “Let’s have a memorial. Let’s talk about it.” Even in my home we didn’t talk about it. My parents never said, are you OK? Do you miss your friends? Are you afraid? I think the reason we didn’t talk about it primarily was because there was nothing we could do about it.

What stands out most about that day?

The first thing that stands out is the pain of that day. How horrible it was and learning that my friends had died. The second thing that stands out is that no one responded. No one did anything. For the first 14 years after the bombing of the church, no one was arrested. Nothing happened. The police and FBI acted as though they didn’t have any evidence or enough evidence. But the police would later say they did not feel they could get a conviction in Birmingham. The mood of the community was such that they did not think white people were going to convict one of their own for the death of black children. But the truth was, in Birmingham, no one thought that black life was important. It didn’t matter that blacks were killed, that little girls were killed in Sunday school.

How did the bombing of 16th Street impact Birmingham?

It gave us a reputation that we didn’t want. There is nowhere in the world that you can go that people don’t know this story. That’s how horrific it was. And how people saw what we had done. When we finally prosecuted someone 14 years later and then 32 years later, I think it was because we received pressure from the rest of the world. You know how people can shame you? You want to make amends. That one image we could never get rid of: killing babies in church all in the name of segregation. So I think when we began the prosecuting of the last two men, it was an attempt to say we have changed. We are a different nation.

What impact did the bombing have on the civil-rights movement and America?

It softened the heart of the oppressors. What Dr. King said to us was that unmerited suffering was always redemptive. He also said that the blood of these girls might well serve as a redemptive force not only for Birmingham, Alabama, but for the rest of the world. We may yet see something very horrible become a force for good. And I think that is what we saw to a large extent. The following year we saw the signing of the civil-rights legislation.

How would you describe Birmingham today?

I think that Birmingham is a city that is on its way. We have not arrived yet. We really have made some good strides toward showing that we value all of our citizens. It’s a place that’s openly integrated now in all aspects. In 2000 we had an amendment on the ballot to remove the ban on interracial marriage. So we just did that in 2000. In the meantime, the state still functions under the 1901 constitution. The governor has put together a commission to rewrite the constitution for Alabama.