The deadliest mass killing in Illinois history took place in the 1920s, but it wasn’t the St. Valentine’s Massacre. It didn’t even happen in Chicago: it happened in Herrin, a small town in Williamson County, in deep Southern Illinois. Most Chicagoans have probably never heard of Herrin, but 100 years ago today, on June 22, 1922, union miners shot and stabbed 21 “scabs” who were shipping coal in violation of a nationwide mining strike. No one was ever punished for the killings, and for decades afterward, no one in Herrin spoke a word about what became known to history as the Herrin Massacre.

Labor militancy has traditionally been a strong passion in Southern Illinois. Paul M. Angle, former director of the Chicago Historical Society and author of Bloody Williamson: A Study in American Lawlessness, which contains the most thorough account of the massacre, believed it defined Williamson County as well as it defined the Appalachian communities from which Southern Illinois drew its early settlers, and with which it shared a dependence on coal.

“We Americans have never been slow to resort to violence, sometimes in passion, sometimes in the conviction that legal processes were either too inadequate or too slow in their operations; sometimes simply because the law interfered with what we want to do,” Angle wrote in 1952. “Williamson County, Illinois, I believe, offers an almost unrivaled setting for a study of this phenomenon. There one can identify a wide variety of its causes—family hatreds, labor strife, religious bigotry, nativistic narrowness, a desire for money and to hell with the rules…With the possible exception of Harlan County, Kentucky, I know of no other American locality possessed of these attributes.”

The United Mine Workers of America had lifted Southern Illinois’s coal miners out of serfdom, raising wages from as low as $2 a day to as high as $15. On April 1, 1922, UMWA president John L. Lewis, whose portrait adorned many miners’ homes, called a nationwide soft coal strike. All the miners went along. So did almost all the mines. All except the Southern Illinois Coal Company, a strip mine that had been opened a year before by William J. Lester, an absentee owner from Cleveland. Recognizing that Lester had just made a large investment, the union gave him permission to mine coal, but not ship it. Desperate to make a profit, and tempted by the high coal prices resulting from the strike, Lester reneged on the deal. He fired his union miners, hired 50 replacements, mostly from Chicago, and shipped out 60,000 tons of coal on June 16.

The union was outraged. When Lester refused to shut down operations, miners held an “indignation meeting” at a cemetery—which turned into a lynch mob. Miners looted Herrin’s hardware stores for guns and ammunition, which they used to besiege the 50 men working at the Southern Illinois Coal Company’s mine. The sheriff, who was running for treasurer that fall, and knew the voters were sympathetic to the union, did nothing to stop the mob. Shortly after dawn, the outgunned strikebreakers and their guards waved a flag of surrender—a cook’s apron tied to a broomstick. They agreed to leave the mine in exchange for safe passage out of the county. This was promised—but the promise was not kept. As the prisoners were led away from the mine, they were intercepted by vigilantes, whose leader declared, “The only way to free the country of strikebreakers is to kill them all off and stop the breed.”

The strikebreakers were harried into a secluded woodland, and ordered to run toward a barbed wire fence: “let’s see how fast you can run between here and Chicago, you damned gutter-bums!” As they fled, the strikers opened fire. Men who fell while fleeing were shot in the head. Six survivors were marched to a cemetery, enduring the beatings of strikers and the taunts of women and children along the way. They were tied together and shot. When three still showed signs of life, a miner opened his pocket knife and cut their throats. Another miner urinated on the bodies.

The dead strikebreakers were buried in a mass grave. The sheriff who had looked the other way was elected treasurer in a landslide. In two trials, the miners involved in the massacre were acquitted by sympathetic local juries. The strike ended, the miners returned to work, and the secrecy that had made it impossible for prosecutors to win a conviction continued for generations.

In 1997—the 75th anniversary of the massacre—WBEZ aired a half-hour long essay by Bradley University professor James Ballowe, whose grandfather was allegedly the vigilante who gave the order to kill all the strikebreakers and “stop the breed.” Ballowe grew up in Herrin in the 1930s and ’40s, but did not learn of the massacre until he left home, and read Angle’s book.

“My grandfather’s role remains shrouded in the absolute silence that descended over Herrin after the massacre,” Ballowe said. “We sometimes met killers in the street, and never knew it.”

The townspeople believed the killings had been justified, because the strikers were defending the jobs that fed their families. Ballowe played a clip from a Herrin Massacre, Paul M. Angle, United Mine Workers of America, John L. Lewis, William J. Lester, James Ballowe on the massacre: “If it hadn’t been for what happened in the ’20s, I don’t think you’d have any union around here at this time,” a retired miner asserted.

“The union became as important to the miners as their religion was, or maybe more important, because it was their livelihood,” Ballowe said.

Only in the last few years, now that the killers—and their children—are dead, has Herrin finally come to terms with the massacre. In the early 2010s, a local historian led an effort to locate the graves of strikebreakers whose bodies had never been claimed by family members. Even then, he was threatened with arrest by Herrin’s mayor. After the search succeeded, though, the town agreed to erect a monument with the names of 17 murdered strikebreakers—Herrin’s first public acknowledgement of the deadliest day in its history, and Illinois’s.