World History

Step 1: Understanding the Origin of May Day:
International Workers' Day, also known as Labour Day or May Day, is celebrated on May 1st in many countries. Its origin lies in the struggle for workers' rights in the 19th century, particularly the demand for an eight-hour workday.

Step 2: Connecting to the Historical Event:
The date was chosen by the Second International, a pan-national organization of socialist and communist political parties, to commemorate the Haymarket Affair.
The Haymarket Affair (or Haymarket Riot) was the aftermath of a bombing that took place at a labor demonstration on May 4, 1886, at Haymarket Square in Chicago, USA. The demonstration began peacefully in support of workers striking for an eight-hour workday, the day after police had killed one and injured several workers. The event became a symbol of the international struggle for workers' rights, and May 1st was chosen to mark the general strike that had begun on that day in 1886 and culminated in the Haymarket Affair.

Step 3: Final Answer:
The celebration of International Labour Day on 1st May is associated with the Haymarket Affair, Chicago.