William Dudley Haywood, nicknamed "Big Bill", was an American labor organizer and founding member and leader of the Industrial Workers of the World (IWW) and a member of the executive committee of the Socialist Party of America. During the first two decades of the 20th century, Haywood was involved in several important labor battles, including the Colorado Labor Wars, the Lawrence Textile Strike, and other textile strikes in Massachusetts and New Jersey.

The Haymarket affair, also known as the Haymarket massacre, the Haymarket riot, the Haymarket Square riot, or the Haymarket Incident, was the aftermath of a bombing that took place at a labor demonstration on May 4, 1886, at Haymarket Square in Chicago, Illinois, United States. The rally began peacefully in support of workers striking for an eight-hour work day, the day after the events at the McCormick Harvesting Machine Company, during which one person was killed and many workers injured. An unknown person threw a dynamite bomb at the police as they acted to disperse the meeting, and the bomb blast and ensuing retaliatory gunfire by the police caused the deaths of seven police officers and at least four civilians; dozens of others were wounded.