The first labor unions arrived in Colorado nearly as quickly as the first coal miners. There were strikes in the Colorado coalfields in 1884, 1894, and 1904. But none rivaled the rebellion of 1914.

Between 1870 and 1910, Colorado’s non-Native American population had multiplied 20 times over. By then, Colorado Fuel & Iron Co. (CF&I) was the largest employer in the state. Its workers were a combination of American-born men of English and Scots-Irish descent and immigrants from places as far-flung as Greece and Japan. Working and living conditions for the thousands of miners were harsh and dangerous. Dynamite explosions, mine collapses, and premature death from work-related illness and injury were common. When an inspector visited the site of a mine explosion that had killed 56 in a coal town called Starkville in 1910, he was startled to see not just how the miners and their families had died, but how they’d lived, writing:

The residences or houses and living quarters of the miners smack of the direst poverty. Practically all of the residences are huddled in the shadow of the coal washers and the smoke of the coke ovens making the surroundings smutty with coal dust and coke smoke. Not all of the houses are equipped with water, and practically none have sewerage; they depend for their water upon hydrants on the streets. The people reflect their surroundings; slatternly dressed women and unkempt children throng the dirty streets and alleys of the camp. One is forced to the conclusion that these people must be very poorly paid, else they would not be content to live in this fashion.

They were not content. The miners agitated for better pay and conditions on their own, but they were repressed at every turn. In Blood Passion: The Ludlow Massacre and Class War in the American West, Scott Martelle writes, “They did not have a political voice. The courts and the local political structure in the south [of Colorado] were directly controlled by, or friendly to, the interests of mine owners. In elections, local mine superintendents often cast their workers’ ballots for them.” Companies like CF&I had undercover detectives and private security who would spy on union organizers and run them out of town. The mine operators would collude with one another, for instance sending letters with warnings like this one: “All superintendents: look out for Jack Nelson, commonly called the Big Swede. He has been working at Wooten and he is an organizer for the U.M.W. of A.” — that is, the United Mine Workers of America (UMW).

The company towns, writes historian Philip Foner, were “feudal domains with the company acting as lord and master. The ‘law’ consisted of company rules. Curfews were imposed, company guards — brutal thugs armed with machine guns and rifles loaded with soft-point bullets — would not admit any ‘suspicious stranger’ into the camp.” CF&I was the most restrictive of all, and its employees often lived 20 to a shack, in houses owned by the company itself.

In 1913, CF&I workers sought representation from the UMW, which had increased its presence throughout the region despite the attempts of company spies to drive them out. In September, after the company refused demands for an eight-hour workday and the elimination of company guards, the workers went on strike. The labor organizer Mother Jones gave a rousing speech in support of the strike, for which she was imprisoned for 20 days. In her autobiography she writes of her time in a Trinidad, Colorado, prison:

Day was perpetual twilight and night was deep night. I watched people’s feet from my cellar window; miners’ feet in old shoes; soldiers’ feet, well-shod in government leather; the shoes of women with the heels run down; the dilapidated shoes of children; barefooted boys. The children would scrooch down and wave to me but the soldiers shooed them off.

When she was released, she saw that the miners had been evicted from their shacks for attempting to strike. They were now living in tent colonies outside the towns of boarded-up shanties they had once called home. Not only that, but the company guards were arresting the newly homeless miners for vagrancy and forcing them to work for no pay as punishment. The miners were regularly beaten by the guards, but still they wouldn’t stop striking. They knew that the only way to get concessions from Rockefeller’s company was to hold out and watch the profits plummet.

A Greek miner shakes hands with a member of the U.S. Fifth Cavalry as he disembarks from a train, arriving in Trinidad, Colorado, to maintain order during the strike. (Bettmann Archive via Getty Images)

Outraged by the workers’ insubordination, CF&I gave its hired thugs — or “detectives,” working for a private security company called Baldwin-Felts — the liberty to try a new tactic: outright terrorism. The Baldwin-Felts detectives began to drive around at night and fire into the tents, terrifying, injuring, and on occasion killing the sleeping miners and their families. The miners organized armed patrols to ward off the detectives, but they were no match for the “Death Special.” That was the name Baldwin-Felts agents gave to the car, equipped with a machine gun, in which they roamed the coalfields at night.

In response to the terrorism of the agents, the miners and their families dug pits in the earth under their tents, in which they hid at night to avoid being sprayed by bullets. They endured this violence, living in their tents with their pits, all through the winter and spring. The few occasions they fired back at agents were used as justification for calling in the Colorado National Guard.

On April 19, the striking miners at Ludlow put on an Orthodox Easter celebration for the Greek families in their tent colony. On April 20, the Colorado Guardsmen came to Ludlow, claiming to be searching for a suspected criminal. It’s still unclear who fired the first shot, but a ten-hour gun battle between the armed striking miners at Ludlow and the Colorado National Guard ensued. Martelle described the scene, which would later come to be known as the Ludlow Massacre: