In early May 1886, Chicago workers demonstrated for an eight-hour workday. One demonstration on May 3, 1886, in solidarity with workers who had been locked outside of the McCormick Reaper Plant while strikebreakers worked inside, led to police opening fire and killing some workers.

To protest those McCormick killings, two thousand workers came to Haymarket Square in the West Loop (Randolph and Des Plaines) to an event which Chicago Mayor Carter Harrison permitted and even attended. As the rally came to an end, Mayor Harrison ordered the police to disperse, yet some 180 police entered the square and began attacking attendees.

At that point, someone threw a bomb at the police. The explosion resulted in a number of deaths; wild gunfire by police killed workers and as many as six police officers. But the bomb galvanized a campaign against organized labor and political radicals. Eight labor organizers were charged with conspiracy and found guilty, even though only one of the eight even attended the rally that night.

A massive international cause célèbre rallied on behalf of the Haymarket Eight. Four of the eight were hanged in 1887, a fifth died in prison, and the remaining three were pardoned by Illinois Governor John Peter Altgeld in a move considered to be Altgeld's swansong in politics.

125 years after that fateful night, the consequences of Haymarket still reverberate. May Day has been celebrated internationally (except in the United States) as a workers' holiday, generations of radicals drew inspiration of Haymarket for their own activism (the logo for Chicago Indymedia recalls this history), and the eight-hour workday was ultimately won. But efforts to improve the lot of poor and workers face constant assault and threats of rollback; the struggles fought in 1886 echo those fought in 2011. But the struggle continues, as it always does.

The city of Chicago did place a memorial to Haymarket which was unveiled on a nondescript Tuesday in September 2004 to comparatively little fanfare. But Chicago citizens and activists have organized memorials and commemorations of the quasquicentennial (125th anniversary) of Haymarket, including a full-scale historical re-enactment at Haymarket Square

Read more: Mayday and the Haymarket Martyrs | 125th Anniversary of Haymarket Affair Celebrates Origin of May Day | Haymarket and the Chicago Idea Resonate 125 Years Later