The 'Haymarket Affair' was the aftermath of a bombing that took place at a labor demonstration on May 4, 1886, at Haymarket Square in Chicago. The riot resulted in the deaths of seven police officers and at least four civilians.
In response to the Haymarket Affair, employers increased anti-union measures, such as firing and blacklisting union members, locking out workers, recruiting strikebreakers; employing spies, thugs, and private security forces and exacerbating ethnic tensions in order to divide the workers.
Here's how it all went down:
On May 3, 1886, one person was killed and several injured as police intervened to protect strikebreakers and intimidate strikers during a union action at the McCormick Harvesting Machine Company that was part of a national campaign to secure an eight-hour workday.
To protest police brutality, anarchist labour leaders called a mass meeting the next day in Haymarket Square. It began as a peaceful rally in support of workers striking.
However, 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 many officers and protesters.
The Chicago Herald described a scene of "wild carnage."
The Haymarket Affair created widespread hysteria directed against immigrants and labour leaders. In the internationally publicized legal proceedings that followed, eight anarchists were convicted of conspiracy. A harsh anti-union clampdown followed. The entire labor and immigrant community, particularly Germans and Bohemians, came under suspicion. Police raids were carried out on homes and offices of suspected anarchists.
The Knights of Labor (KOL), at the time the largest and most successful union organization in the country, was blamed for the incident.