The rally at Haymarket Square was winding down. The crowd, initially several thousand, had thinned to a few hundred as weather deteriorated. Mayor Carter Harrison had stopped by, judged the gathering peaceful, and walked home. The final speaker, Methodist pastor Samuel Fielden, was delivering a brief ten-minute address when police arrived in force at about 10:30 PM, marching in formation and ordering dispersal. Seconds later, a homemade fragmentation bomb arced through the air and detonated among the advancing officers, killing patrolman Mathias Degan instantly. Then the shooting began. Police fired into the crowd, reloaded, and fired again. An anonymous officer later told the Chicago Tribune that "a very large number of the police were wounded by each other's revolvers." In less than five minutes the square was empty except for the dead and dying -- seven policemen and at least four workers killed, with dozens more wounded on both sides.

Police launched an eight-week dragnet, ransacking meeting halls and homes without warrants. Eight men were indicted -- not for throwing the bomb, but as accessories to murder. Only two had been present when it exploded. The lead suspect, Rudolf Schnaubelt, fled the country. The trial, presided over by Judge Joseph Gary, became a spectacle of prejudice. Jury selection lasted three weeks with nearly a thousand candidates called; all union members and socialist sympathizers were dismissed, yet most seated jurors openly confessed bias. A bailiff was appointed who handpicked jurors likely to convict. The jury found all eight guilty. Seven received death sentences. Historian Carl Smith later wrote: "The visceral feelings of fear and anger surrounding the trial ruled out anything but the pretense of justice right from the outset."

Governor Richard Oglesby offered clemency to any who asked, but four refused on principle -- they had committed no crime. Only Fielden and Schwab requested mercy and had their sentences commuted to life. Louis Lingg, the youngest defendant, died by suicide in his cell the night before his execution using a smuggled blasting cap. The next morning, Engel, Fischer, Parsons, and Spies went to the gallows in white robes, singing the anthem of the international revolutionary movement. Witnesses reported the condemned men did not die instantly but strangled slowly, visibly shaking the spectators. Six years later, in 1893, progressive Illinois Governor John Peter Altgeld pardoned the surviving prisoners, calling them victims of "hysteria, packed juries, and a biased judge" and noting the state had never identified the actual bomber.

The Haymarket affair divided the nation. Newspapers branded the defendants "bloody monsters" and "dynamarchists," while labor supporters worldwide elevated them to martyrdom. Oscar Wilde, Clarence Darrow, and George Bernard Shaw condemned the trial. In 1889, the International Socialist Congress chose May 1 as International Workers' Day to commemorate the broader eight-hour-day strikes that preceded Haymarket. Today, more than eighty countries celebrate May Day as a labor holiday -- every one of them tracing the tradition back to this corner of Chicago. The irony is that the United States, where it all began, celebrates Labor Day in September instead.

The original Haymarket Square at Randolph and Desplaines streets in Chicago's West Loop looks nothing like it did in 1886. A bronze sculpture by Mary Brogger, installed in 2004, depicts a wagon -- evoking the speakers' platform from that night. The Haymarket Martyrs' Monument at Forest Home Cemetery in the suburb of Forest Park, where the executed men are buried, was designated a National Historic Landmark in 1997. It remains a pilgrimage site for labor activists from around the world. The square itself sits amid restaurants and loft conversions, a quiet stretch of city where most passersby have no idea they are walking across ground that changed the history of work.