On May 4, 1886, a bomb exploded during a labor demonstration near Haymarket Square. The ensuing gunfire and chaos brought a grisly end to what began as peaceful support for an eight-hour workday and led to the trial and execution of rally organizers. The incident also drew irrevocable attention to a conversation about workers rights and the role of law enforcement that continues today. In this guide to the key moments and sites of one of Chicago’s most confusing and chaotic events, author Joseph Anthony Rulli aims to establish a clearer understanding of its historical significance.