The Haymarket affair (also known as the Haymarket massacre or Haymarket riot) was the aftermath of a bombing that took place at a labor demonstration on Tuesday May 4, 1886, at Haymarket Square in Chicago. It began as a peaceful rally in support of workers striking for an eight-hour day and in reaction to the killing of several workers the previous day by the police. An unknown person threw a dynamite bomb at police as they acted to disperse the public meeting. The bomb blast and ensuing gunfire resulted in the deaths of seven police officers and at least four civilians; scores 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. 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.
The Haymarket affair is generally considered significant as the origin of international May Day observances for workers. The site of the incident was designated a Chicago Landmark in 1992, and a public sculpture was dedicated there in 2004. In addition, the Haymarket Martyrs' Monument at the defendants' burial site in nearby Forest Park was designated a National Historic Landmark in 1997.
"No single event has influenced the history of labor in Illinois, the United States, and even the world, more than the Chicago Haymarket Affair. It began with a rally on May 4, 1886, but the consequences are still being felt today. Although the rally is included in American history textbooks, very few present the event accurately or point out its significance," according to labor studies professor William J. Adelman.
- The Haymarket Affair, Chicago, 1886: The Great Anarchist Riot and Trial (A Focus Book) - Corinne J. Naden
- The history of the Haymarket affair;: A study in the American social-revolutionary and labor movements - Henry David