The 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 Square 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.