In 1884, a labor organization in the U.S. (predecessor to the AFL) decided to organize workers around the demand for an 8-hour day (instead of the 12, or 14-hour days which were the regular working hours for most American workers). They planned to spend 2 years educating and organizing workers around this issue and then, on May 1, 1886, hold a nationwide strike to demand the 8-hour day as well as other rights for working people.
As it turns out, in Chicago, the workers at a plant owned by McCormick were on strike right before May 1, 1886, came around. The company owner had replaced all the workers with scabs, and locked out the regular workers. One evening when the scabs left work, the regular workers met them and there were fights and skirmishes. The police sided with the business owner, and shot and killed several of the workers.
(Drawing of police shooting workers)
This was followed immediately by the planned labor demonstration on May 1, 1886, and 80,000 people in Chicago marched for labor rights exactly as the organizers had planned. The local rich people and business owners were horrified at the idea that they might be stopped from using their workers as slave labor, forcing them to work however many hours that they demanded. So the local business owners demanded that the police get tough on the labor organizers, and shut down their efforts to organize to demand the 8-hour day.
The labor and other political organizers called for a mass meeting on May 4 to protest the police killing of workers on strike at McCormick. The meeting was scheduled to be held in the Chicago haymarket. A large crowd gathered in the street to hear the speakers for the meeting, but rain began to fall. Towards the end of the meeting, 200 local police massed on one end and began demanding that the workers break up immediately. Just then, somebody threw a bomb right in the middle of where the police were standing. The police panicked and began firing at random into the crowd of workers, killing several workers. Several police were also killed, one from the bomb and the rest supposedly by friendly fire (in their panic, they shot their own people by mistake).
The right-wing and the business owners seized on this incident, lied about what had really happened, began calling it "The Haymarket Riot" to suggest that workers who try to organize for their rights are all crazed bomb-throwing gun-shooting lunatics, and used the fear they created to crack down on labor unions and organizations across the country.
Because of this effort by the right-wing, the push for an 8-hour day was ended in its tracks. The 8-hour day did not become an official part of American workers' rights until fifty years later, in 1935.
(The Haymarket gathering)
Seven labor organizers in the Chicago area including Albert Parsons, including people who had not even been present at the Haymarket that night, including people who had no involvement in the meeting, were prosecuted in bogus show-trials. The prosecution's theory was that labor organizers were responsible for any violence that happened at a labor rally because, by encouraging working people to stand up for their rights, they were essentially encouraging violence. It was a disgusting and disgraceful misuse of our criminal injustice system. The real point of the trial was to shut down the efforts of the labor movement, and give a fierce warning to workers everywhere that if they stood up for their rights, they would be murdered by the state. There was never any evidence introduced at the trial, or later, to show that any of these 7 (later called the "Haymarket Martyrs") had any involvement with the bomb, or ever did anything to encourage violence.
On June 26, 1894, Governor John Peter Altgeld of Illinois found that the trial of the Haymarket Market Martyrs had been grossly unfair, and he pardoned all seven of the defendants. It did no good to the five who were already dead: Parsons, Spies, Fischer and Engel had already been hanged, and Lingg supposedly committed suicide in his cell.
In 1889, the AFL sent a delegate to the international labor conference in Paris, to urge that May 1 of each year thereafter be celebrated as a day of labor solidarity. That proposal was adopted, and May 1 is considered International Workers' Day or Labor Day, an official holiday, for most nations in the world. Except the United States, which did not want to encourage working people to remember the history of labor struggles. So our Labor Day is in September and commemorates nothing more than having a bar-be-que before the kids start back to school.
Monument to the Haymarket Martyrs: