Strikes by industrial workers were increasingly common in the United States in the 1880s, a time when working conditions were often dismal and dangerous and wages were low.

The American labor movement during this time also included a radical faction of socialists, communists and anarchists who believed the capitalist system should be dismantled because it exploited workers. A number of these labor radicals were immigrants, many of them from Germany.

The May 4, 1886, rally at Haymarket Square was organized by labor radicals to protest the killing and wounding of several workers by the Chicago police during a strike the day before at the McCormick Reaper Works.

Anarchist leader August Spies, a German immigrant, was among the many people who were angered by the police’s reaction to the McCormick strike. He had been giving a speech to strikers a short distance from the factory and had witnessed police open fire on workers.

Spies rushed to the offices of the Arbeiter-Zeitung, an anarchist newspaper he edited, and wrote a leaflet denouncing the incident. He headlined the flier “Workingmen, To Arms.” That evening, as word of the McCormick killings spread, another group of Chicago anarchists planned an outdoor rally to protest police brutality. They scheduled the gathering for the following evening at Haymarket Square, a large space on Desplaines Street.

Around 8:30 p.m. on May 4, the streets near Haymarket Square swelled with some 2,000 workers and activists. August Spies opened the rally by climbing atop a hay wagon and giving a speech on the “good, honest, law-abiding, church-going citizens” who had been attacked at the McCormick factory. He was followed by Albert Parsons, a former Confederate soldier turned radical anarchist. Chicago Mayor Carter Harrison was even in attendance to ensure the protest was peaceful.

Toward the end of the Haymarket Square rally, a group of policemen arrived to disperse the crowd. As the police advanced, an individual who was never identified threw a bomb at them. The police and possibly some members of the crowd opened fire and chaos ensued. Seven police officers and at least one civilian died as a result of the violence that day, and an untold number of other people were injured.

The Haymarket Riot set off a national wave of xenophobia, as scores of foreign-born radicals and labor organizers were rounded up by the police in Chicago and elsewhere. In August 1886, eight men labeled as anarchists were convicted in a sensational and controversial trial in which the jury was considered to be biased and no solid evidence was presented linking the defendants to the bombing.

Judge Joseph E. Gary imposed the death sentence on seven of the men, and the eighth was sentenced to 15 years in prison. On November 11, 1887, four of the men were hanged.

Of the additional three who were sentenced to death, one committed suicide on the eve of his execution and the other two had their death sentences commuted to life in prison by Illinois Governor Richard J. Oglesby. The governor was reacting to widespread public questioning of their guilt, which later led his successor, Governor John P. Altgeld, to pardon the three activists still living in 1893.

In the aftermath of the Haymarket Riot and subsequent trial and executions, public opinion was divided. For some people, the events led to a heightened anti-labor sentiment, while others (including labor organizers around the world) believed the men had been convicted unfairly and viewed them as martyrs.