Haymarket Square Riot is a rebellion and an outbreak of violence in Chicago on May 4, 1886. Due to the ever-expanding demands for eight-hour working hours, demonstrations were held on the Haymarket market, organized by a group of anarchists. In a controversial judgment, eight men were sentenced, seven were sentenced to death and one to 15 years in prison. This riot brought the greatest damage to the workers' movement in the United States, The Knight of Labor at that time was the biggest and most successful union organization blamed for the incident. Although the public immediately after the incident was on the side of the police and against the workers 'demands, the struggle of the workers' organizations and trade unions continued for the purpose of eight-hour working hours. Thus, the Socialist International decided to hold demonstrations all over the world on May 1, 1890, as a reminder of the dead and condemned anarchists on May 4, 1896, and to continue the struggle to meet the demands of workers.