Haymarket affair
The Haymarket Affair was a bombing that took place at a labor demonstration on May 4, 1886, at Haymarket Square in Chicago. The rally began peacefully in support of workers striking for an eight-hour work day; it was held the day after a May 3 rally at a McCormick Harvesting Machine Company plant on the West Side of Chicago, during which two demonstrators had been killed and many demonstrators and police had been injured.