First United States Labor Day Parade, September 5, 1882, in New York City. Labor Day in the USA is a public holiday celebrated on the 1st Monday in September. It honors the American labor movement and the contributions that workers have made to the strength, prosperity, and well-being of their country. Labor Day was promoted by the Central Labor Union and the Knights of Labor, who organized the first parade in New York City.
The Haymarket affair (also known as the Haymarket massacre or Haymarket riot) was the aftermath of a bombing that took place at a labor demonstration on Tuesday May 4, 1886, at Haymarket Square in Chicago. It began as a peaceful rally in support of workers striking for an eight-hour day and in reaction to the killing of several workers the previous day by the police. An unknown person threw a dynamite bomb at police as they acted to disperse the public meeting.