Haymarket affair

The Haymarket Massacre was the aftermath of a bombing that took place at a labor demonstration on May 4, 1886, at Haymarket Square in Chicago. It began as a peaceful rally in support of workers striking for an eight-hour work day, the day after police killed one and injured several workers. An unknown person threw a dynamite bomb at the police as they acted to disperse the meeting, and the bomb blast and ensuing gunfire resulted in the deaths of seven police officers and at least four civilians; dozens of others were wounded.

In the internationally publicized legal proceedings that followed, eight anarchists were convicted of conspiracy. The evidence was that one of the defendants may have built the bomb, but none of those on trial had thrown it. Seven were sentenced to death and one to a term of 15 years in prison. Illinois Governor Richard J. Oglesby commuted two of the sentences to terms of life in prison; another committed suicide in jail rather than face the gallows. The other four were hanged on November 11, 1887. In 1893, Illinois Governor John Peter Altgeld pardoned the remaining defendants and criticized the trial.

Wikipedia