Why were the 1920s such a tough time for America’s labor unions?

Call it a backlash against their growing strength. After expanding power during the Progressive Era in the first two decades of the 20th century, organized labor strengthened further during World War I. The U.S. government took a more conciliatory approach toward labor unions to prevent work stoppages that could disrupt the war effort. In return for a moratorium on strikes, unions received shorter workdays, greater collective bargaining rights and seats of power in federal wartime agencies such as the National War Labor Board, which mediated labor disputes. As a result, membership in the American Federation of Labor (AFL), the country’s largest labor union, surged by 50 percent between 1917 and 1919.

After World War I, however, the labor movement lost ground. The National War Labor Board disbanded, and American businesses sought to regain power over the unions. “As soon as the armistice was signed in November 1918, their pushback against workers’ gains began,” says Georgetown University labor historian Joseph McCartin. “Meanwhile, workers’ expectations had risen as a result of wartime gains, and they were not in a mood to give up those gains. This set the stage for a titanic struggle in 1919, the biggest eruption of labor unrest to that point in history.”

Inflation eroded American workers’ purchasing power in the months after the war. Food prices more than doubled and clothing prices more than tripled between 1915 and 1920. But most businesses refused to boost wages accordingly.

In response, over 3,500 work stoppages involving more than 4 million workers occurred in 1919. That February, labor unions across Seattle halted work in solidarity with 35,000 shipyard workers who had walked off the job in the first general (or cross-industry) strike in American history. That fall, nearly 400,000 members of the United Mine Workers of America went on strike, as did 365,000 steelworkers across the Midwest who attempted to unionize.

Striking workers, however, won few concessions. Having endured rationings and shortages during the war and the 1918-19 Spanish flu pandemic, an exhausted American public felt little solidarity with an increasingly militant labor movement. Attitudes further turned against organized labor when the police force in Boston went on strike and sparked fears about public safety. “When the big union drives in steel, electrical manufacturing and meatpacking were crushed by the strikebreaking of 1919, all of labor was on the defensive going into the 1920s,” McCartin says.

In the wake of the 1917 Russian Revolution and other communist uprisings in Europe, many middle- and upper-class Americans began to equate unionism with Bolshevism. Some believed labor leaders sought nothing less than to overthrow the American capitalist system. Amid this “Red Scare,” industrialists branded union members as anti-American radicals. The New York Times wrote of the Great Steel Strike of 1919: “It is industrial war in which the leaders are radicals, social and industrial revolutionaries.” Those concerns only grew after several mail bombs were sent to government officials, industrialists and perceived foes of organized labor in the spring of 1919, and an explosive device killed more than 30 people outside the Wall Street headquarters of J.P. Morgan and Co. on September 16, 1920.

“The union movement itself became quite conservative in reaction to the Red Scare,” says Nelson Lichtenstein, a historian at the University of California, Santa Barbara. He says worries about the possible radicalism of unskilled immigrant workers led the AFL and craft unions to focus instead on the organization of skilled workers and more conventional union activities. “It‘s a period when ethnic tensions are very high, and the working class in many mass-production industries such as steel are often immigrants,” says Lichtenstein. “The hostility of craft unions [devoted to a single trade] to the idea of big [multi-trade] industrial unions with lots of immigrant workers persisted in the 1920s.”

Americans voted for a “return to normalcy” in 1920 with the election of Warren G. Harding, the first of three pro-business Republican presidents to occupy the White House in the 1920s. After a series of progressive presidencies, the playing field once again tilted toward employers. “The chief business of the American people is business,” declared Calvin Coolidge, who succeeded Harding after his death in 1923.

Throughout the 1920s, courts regularly issued injunctions against striking, picketing and other union activities. When 400,000 railroad shopmen walked off their jobs after the Railroad Labor Board slashed their wages in 1922, Attorney General Harry Daugherty won a sweeping injunction to crush the nationwide strike. “So long and to the extent that I can speak for the government of the United States, I will use the power of the government to prevent the labor unions of the country from destroying the open shop,” he declared.

The U.S. Supreme Court issued a string of anti-labor decisions during the 1920s, says McCartin: Duplex Printing Press Co. v. Deering (1921) punched a fatal hole in the Clayton Act’s protections for labor. Truax v. Corrigan (1921) prevented states from limiting employers’ use of injunctions to crush strikes. And Adkins v. Children’s Hospital (1923) invalidated minimum-wage laws that protected women workers.

With the labor movement weakened, union membership plunged in the 1920s from 5 million to 3 million. Business profits, meanwhile, soared. The decade saw an accumulation of wealth that harkened back to the Gilded Age. Approximately 200 corporations controlled half of the country’s corporate wealth. Even though U.S. Steel, the country’s largest employer, saw its profits double between 1924 and 1929, workers didn't receive a single general wage increase.

Following the onset of the Great Depression, however, organized labor rebounded as President Franklin D. Roosevelt advanced his New Deal program, which brought new protections that led to a new surge in union membership.