Dr. Martin Luther King Jr. spent his final full day on earth advocating for the rights of workers in what’s now known as his “I’ve Been to the Mountaintop” speech. It was April 3, 1968, and King stood up at the Mason Temple in Memphis, Tennessee, and spoke in support of the city’s 1,300 sanitation workers, who were then on strike fighting for better safety standards, union recognition, and a decent wage — a work stoppage that was inspired partly by the deaths of Echol Cole and Robert Walker, who had been crushed to death by a garbage truck.

“We've got to give ourselves to this struggle until the end,” he told the assemblage. “Nothing would be more tragic than to stop at this point, in Memphis. We've got to see it through. And when we have our march, you need to be there. Be concerned about your brother. You may not be on strike. But either we go up together, or we go down together.”

His emphasis on supporting striking workers helped to illustrate just how firmly enmeshed the labor movement was with the greater struggle for civil rights. The 1963 March on Washington for Jobs and Freedom (generally known as the March on Washington) was organized by a coalition of six organizations, known as the Big Six — the Student Nonviolent Coordinating Committee, the Congress on Racial Equality, the Southern Christian Leadership Conference, the National Association for the Advancement of Colored People, the Brotherhood of Sleeping Car Porters, and the National Urban League. The Brotherhood of Sleeping Car Porters was the first predominantly black labor union to be chartered by the American Federation of Labor (AFL) and was founded by A. Philip Randolph, a major leader in both the civil rights movement and the wider American labor movement. A labor union’s purpose is to improve wages, hours, and working conditions within a workplace, and it uses workers’ collective power to bargain for a legally binding contract between them and their employer — and given the rampant discrimination and racism that black workers faced, they had much to gain by organizing.

In 1941, Randolph joined forces with organizer Bayard Rustin — one of the civil rights movement’s lesser-known but pivotal figures, whose status as a gay man often saw him unjustly relegated to behind-the-scenes roles — and threatened to bring a 100,000-person march to Washington unless President Franklin D. Roosevelt ended racial segregation in the defense industries. They won that battle, and in 1955, Rudolph became the vice president and member of the executive council of the AFL-CIO. His tenure there helped to spotlight one of the enduring issues within the wider labor movement: racism and discrimination. At the time of the Brotherhood’s founding, in 1925, half the affiliates of the AFL barred black people from membership.

In 1963, Rudolph and Rustin led the planning for the March on Washington. They applied the lessons they’d learned 20 years prior, swelling the ranks to at least 250,000 by encouraging nonblack participants to come. By then, Rudolph had been organizing black workers and fighting against occupational Jim Crow laws for over 50 years.

In 1965, he and Rustin founded the A. Philip Randolph Institute to “continue the struggle for social, political and economic justice for all working Americans,” as their website says. As Randolph once said, “Justice is never given; it is exacted and the struggle must be continuous for freedom is never a final fact, but a continuing evolving process to higher and higher levels of human, social, economic, political and religious relationship.”