May Day, as it is known now, is an international holiday celebrating organized labor following the Haymarket Affair in 1886. The event was an outbreak of violence by police against labor unionists following a mysterious pipe bomb explosion (probably started by the own police). Following the explosion, a gunfight ensued with the police firing on the crowd, and even some workers firing back. The only ones punished for this were the organizers of the rally, all of them anarchists (who were the “terrorists” of the 19th century, largely scapegoats). anthropophagous: [via]