Ancient Celts and Saxons celebrated May 1st with games and feasts to mark the end of winter. Although it was later outlawed by the Catholic church, the tradition continued in England.
Today it is known as the international working class holiday - this stems from the struggle for an eight hour working day - on this day in 1886 demonstrations took place in Chicago Haymarket Square and several people were killed. Three years later International Working Men's Association designated May 1st to be an international holiday in commemoration of Haymarket events. The red flag symbolizes the working class martyrs' blood spilled in battle for workers rights.