On the holiday we honor Martin Luther King, we might want to reflect on the history the propelled Dr. King to the forefront of the civil rights movement and recall the many people who worked and sacrificed so that Dr. King could do what he needed to do.

Sometimes, we tend to think of Dr. King and Rosa Parks as unique figures in history, rather than symbolic figures of the thousands of people before them who lead the way and struggled for more than a century so that one day Rosa Parks could sit where she wanted on the Montgomery bus and Dr. King could deliver his powerful “I Have a Dream” speech to the nation in front of the Lincoln Memorial.

Two pivotal events in the civil rights movement were World War I and World War II. African American veterans returning from fighting the “war to end all wars” and to protect democracy for the world, felt their community should benefit from the same ideals for which they fought. The same is true of World War II vets.

They pushed forward, individually and as groups, to reverse the tide of white supremacy and undo America’s version of institutional apartheid and its Jim Crow laws. One of their main efforts was to end lynching, especially in the South.

Between 1877 and 1950, nearly 4,000 African Americans were lynched; and some, burned dead or alive. These racial terror lynchings were horrific public spectacles that typically escalated into large-scale violence against the entire African American community. Between 1915 and 1940, the victims tended to be sharecroppers seeking to break free of their slave-like existence, ministers, and community leaders who resisted mistreatment.

And some white Americans, who tried to assist and defend their black compatriots, also were murdered or deprived of their economic wherewithal.

Gradually, though, they changed the course of history. The NAACP, African American newspapers, and clergy and lawyers provided leadership, along with enormously courageous individuals.

They helped build the walking bridge, one plank at a time, over the chasm with its river of raging racism and abject poverty raging below. Many sacrificed their lives and livelihood. Many fell into the chasm, blown off the bridge by the fierce winds of hatred.

But they continued to build the bridge. In one instance, in 1939, internationally-famed singer Marian Anderson, after Washington’s concert halls rejected her because of her race, performed before a crowd of 75,000 at the Lincoln Memorial. One wonders if Dr. King heard her melodies wafting in the air a quarter-century later when he stood in the same venue before 250,000 civil rights supporters.

Because of the work and sacrifice of others, Dr. King was able to walk far enough out on the bridge to see the Promised Land on the other side. He helped build on what others had done and made the bridge stronger. But it is not finished.

Our task, as he would certainly tell us today, is to keep working on the bridge. As Michelle Alexander has chillingly pointed out in The New Jim Crow, our criminal justice system continues to disenfranchise the African American community. One way is to heavily penalize minor non-violent drug use, which undercuts and derails individuals’ ability to find meaningful employment. That, in turn, keeps the community impoverished and deprived of opportunity for advancement. Substandard and unequal educational opportunities cause similar damage.

The Martin Luther King holiday is a good occasion to take stock of what we can do as individuals and society to build out the bridge and strengthen it. That is the least we owe to those who sacrificed so that we could be where we are today.