During a labor demonstration on Tuesday May 4, 1886, at Haymarket Square in Chicago, what started as a peaceful rally in support of workers striking for an eight-hour day, turned vilolent when someone threw a dynamite bomb at police as they tied to disperse the public meeting. The bomb blast and gunfire caused the death of seven police officers and at least four civilians, and wounded scores of other people.
In the trial that followed, eight anarchists were convicted of conspiracy, although the prosecution conceded that it could not prove that any the defendants had thrown the bomb seven anarchists were sentenced to death and one to a term of 15 years in prison. The death sentences of two of the defendants were commuted by Illinois governor Richard J. Oglesby to terms of life in prison, and another committed suicide in jail rather than face the gallows. The other four were hanged on November 11, 1887. In 1893, Illinois' new governor John Peter Altgeld pardoned the remaining defendants and criticized the trial.