Correction: This piece has been updated to make clear that the Industrial Workers of the World (IWW) remains in existence. Additionally, an earlier version incorrectly stated that Joe Hill was executed by hanging. The piece has been updated to reflect that Hill was, in fact, executed by firing squad.

Today marks the 100th anniversary of a key event in American labor history: the Centralia massacre.

It was actually less a massacre and more a shootout between the American Legion and the Industrial Workers of the World (IWW), a radical union whose members were better known as Wobblies. Taking place in Centralia, Wash., the conflict resulted in the death of four Legionnaires and the lynching of one IWW member. Although Centralia’s Wobblies claimed they had acted in self-defense, a jury convicted seven Wobblies of inciting violence at Centralia, and the federal government began a massive effort across the nation to try to wipe out working-class radicalism.

Though it happened a century ago, the Centralia massacre still has lessons for today: When fears of immigrants, outsiders and others dominates politics, violence and repression soon follow.

The Centralia massacre occurred at the tail end of the largest immigration wave in American history. Between 1880 and 1924, more than 20 million people came to the United States, mostly from Eastern European and Mediterranean countries. While these immigrants filled the hardest, lowest-paying and most dangerous jobs in America’s industries, native-born whites had little sympathy for them. Instead, native-born whites imagined all sorts of intellectual and physical differences between themselves and these immigrants that, they said, justified their economically marginal positions.

Nativist conspiracy theories also fueled anti-immigrant sentiment. Industrialists like Henry Ford and leading thinkers like Madison Grant imagined that the pope or mysterious Jewish cabals were planning to overrun America with immigrants. Even President Theodore Roosevelt worried that white Americans were committing “race suicide,” effectively allowing themselves to be outbred by more reproductively fecund immigrants.

The IWW challenged these ideas, however. Unlike most labor unions in the early 20th century, which excluded everyone except native-born, white, skilled men, the Wobblies swung their doors wide open to any and all workers, immigrant and native-born alike. The Wobblies said the entire working-class, regardless of race, ethnicity and gender, suffered equally under capitalism and had much to gain by working together to overthrow it.

The union’s anti-capitalist politics and policy of inclusion quickly earned it the ire of business magnates and politicians. Employers in the early 20th century maintained their power by keeping workers divided. As long as white workers fought black workers and immigrant workers fought native-born workers, no one was fighting the boss. Political leaders who were often beholden to America’s industrialists were just as invested in maintaining this system.

The Wobblies threatened to undo this order.

The IWW eventually spread throughout the country, but no matter where it went, conflict and violence often followed. In Utah, the famous Wobbly Joe Hill was arrested, convicted and executed by firing squad on a flimsy murder charge in 1915. Five Wobblies were killed in the Everett massacre of 1916. Seventeen IWW members were tarred and feathered in Tulsa in 1917. That same year, more than 1,000 Wobblies were rounded up, put on a train car, then taken to and left in the middle of the desert after they’d tried to organize a union in Bisbee, Ariz.

World War I only intensified native-born Americans’ disdain for the IWW. Many white Americans believed the war had been started by the sort of Eastern European radicals that the IWW was now organizing and that their continued activism threatened to bring that disorder to America’s shores. Yes, Woodrow Wilson said it was a war to “make the world safe for democracy” — but he didn’t believe immigrants should be equal participants in that democratic order. “Any man who carries a hyphen about with him,” Wilson said, “carries a dagger that he is ready to plunge into the vitals of the Republic when he gets ready.”

In places like Centralia, where the strength of the timber industry gave birth to a strong IWW presence, this heightened combination of nativism and WWI-fueled xenophobia proved deadly. Nov. 11, 1919, was supposed to be a celebration in Centralia. The town’s American Legion had organized a parade of World War I veterans through town. Yet many of Centralia’s World War I veterans were not in a celebratory mood. As they saw it, the Wobbly’s continued presence in town was an affront to their efforts in the war against outside forces of radicalism.

The Armistice Day parade through town started peacefully enough. Initially the marchers followed the intended parade route, right through downtown. But then the parade’s marchers diverted course and marched several blocks, right to the IWW hall.

Centralia’s Wobblies knew the march was probably the prologue to violence, and they’d armed themselves as a precautionary measure. For several tense minutes, Wobblies and Legionnaires traded insults and taunts. Then someone — we don’t know who — opened fire. A melee of bullets followed, and when the shooting finally ended, four Legionnaires were dead.

Local law enforcement showed up and charged the IWW hall, arresting most of the union’s members. One Wobbly, Wesley Everest, made a break for it, killing one police officer before he was finally caught and put in jail. That evening, the lights in Centralia suddenly went out. When they came back on, Everest’s dead body was hanging from a bridge in town.

That the Wobblies acted more out of self-defense than aggression didn’t matter much in the aftermath. The press told a story about the Wobblies as violent, bomb-throwing radicals intent on upending the American political and economic order. It was a story many Americans, primed by decades of xenophobia, nationalism and conspiracy theories about immigrants were willing to buy.

One of those was a young man, fresh out of law school and recently hired by the Justice Department: J. Edgar Hoover. Hearing of the massacre, he convinced his boss, Attorney General A. Mitchell Palmer, that the Wobblies were driving the country into chaos and that they needed to be stopped. With Palmer’s approval, Hoover orchestrated raids on IWW halls across the country.

The Palmer Raids marked the beginning of America’s First Red Scare, a roughly two-year period when the federal government jailed Wobblies and other radical activists on contrived charges, deported immigrant radicals, and raided the halls and meeting places of several unions, all with the goal of wiping out working-class radicalism.

The raids earned Hoover esteem in the ranks of federal law enforcement, and in 1924 he became director of the FBI, where he continued to suppress radical movements, from the American Communist Party in the 1950s to civil rights activists in the 1960s and 1970s.

The Centralia massacre thus marked the end for the IWW as a major force in American politics and a new era of political repression in America. Today it should remind us that when a nation lets fear drive its politics, suppression soon follows.

But even if the Wobblies went into decline after Centralia, their message of inclusion and working-class solidarity across race, gender and ethnicity continued to inspire activists for decades to come. Union activists in the Depression era, student activists in the 1960s and anti-apartheid activists in the 1980s all evoked the memory of Centralia and the Wobblies as a reminder that their struggles were part of a rich tradition of American radicalism that, though repressed, was never eradicated.

So at the same time that we might remember the massacre today as a morality tale about the dangers that lurk behind xenophobia and nationalism, it should also remind us of the potential power people have when they unite against these forces.