Labor and civil rights organizations in the United States often stand shoulder-to-shoulder on a range of issues, but that solidarity has not always been the norm.

The first national labor federation in the U.S., the National Labor Union, was founded a year after the abolition of slavery in 1865, when millions of newly freed black people to were effectively allowed to enter the broad labor force. African-American leaders recognized that their new political rights would not mean much without jobs and economic stability. But although these two nascent communities — labor unions and newly freed former slaves — would seem to be natural allies, they weren’t.

“The assumption of black inferiority was not quite ubiquitous but pretty extensive,” said Eric Arnesen, a professor of history at George Washington University whose work focuses on race, labor, politics and civil rights. “White organized labor shared the view of African-Americans held by most other white Americans, and that shouldn’t be surprising at all.”

Many unions excluded blacks from key sectors of the labor market or restricted them to the least-desirable jobs, fearing they would undercut wages and working conditions. “With few exceptions, there was no solidarity across racial lines,” Arnesen said. “The relationship to African-American workers was at best indifferent and more often hostile.”

Not surprisingly, African-Americans regarded unions mostly negatively, as institutions that excluded blacks. The civil rights pioneer Booker T. Washington urged black workers to avoid unions and even to break strikes to secure jobs otherwise closed to them. When African-Americans wanted to organize, they created their own unions. In 1869, African Americans founded the Colored National Labor Union after the National Labor Union refused to accept black delegates.

But in these early years after the Civil War, the vast majority of African-Americans lived and worked in the agricultural South — not the industrial North, where organized labor was gaining ground — so unions had little relevance to their lives. A notable exception was Alabama, where coal and steel industrialists exploited the Ku Klux Klan's anti-immigrant and anti-Catholic sentiments to undermine solidarity between American-born white Protestants and immigrant Catholics. With the Klan's history of violence against Southern blacks, the potential for labor solidary across racial lines was remote.

Organizing the black labor force became more urgent after the Great Migration, in which millions of African-Americans headed north in the first decades of the 20th century. In the cities, black workers began to protest barriers to jobs and employment discrimination, including those imposed by the unions themselves. Black civil rights organizations (the NAACP was founded in 1909) offered a platform to address labor rights concerns. A. Philip Randolph, who organized the Brotherhood of Sleeping Car Porters in 1925, was a key figure in bringing the two struggles together and winning the support of middle-class African-Americans, Arnesen says. Randolph successfully fought against the Pullman Company’s efforts to block the union and, in 1937, the porters’ union became the first black labor group to align itself with the American Federation of Labor. The other big labor alliance, the Congress of Industrial Organizations, had officially championed inter-racial solidarity since the 1930s, although in practice the track record of their member unions was uneven.

The Great Depression and the industrial mobilization of World War II galvanized the labor movement, and the alliance between civil rights and labor rights groups deepened in the 1940s. They came together to push for fair employment laws, eventually realized with the 1964 Civil Rights Act, and labor organizations to varying degrees supported the African-American struggle for full citizenship. The two movements have often walked the same path. Following are some of the seminal moments in their journey: