The tents huddled together on the high prairie. For seven months, they had borne deluge, frost and blizzard. In that time, the occupants—more than 1,000 striking coal miners and their families—had also endured the fear and fact of violence. On April 20, 1914, the sun rose at 5:20 am. It was the 209th daybreak over the tent colony at Ludlow, Colorado. And it was also the last.

The next twenty-four hours, in which roughly a score of people were killed, would be the bloodiest in the entire sanguinary history of the American labor movement. Immortalized as the Ludlow Massacre, its causes and ramifications have been discussed, disputed and decried for a century. As with the Triangle Shirtwaist Fire of 1911 or the Haymarket Riot of 1886, it generated martyrs, villains, monuments, social legislation and mass movements.

For years, the Ludlow Massacre was a touchstone of our radical tradition. Its legacy was fashioned and sustained by some of the brightest publicists of the left, including John Reed, “Mother” Bloor, Upton Sinclair, Woody Guthrie, George McGovern and Howard Zinn. “It was a watershed event,” wrote novelist and historian Wallace Stegner. Ludlow, he thought, had touched “the conscience of the nation, and if it did not make raw corporate gun-law impossible, it gave it a bad name. At the very least, it made corporations more careful.”

The union movement drew enough strength from the events at Ludlow—as well as its defeats and victories on untold shop floors across the country—to force the implementation of new forms of welfare support and working-class power. In the 1930s and ’60s, the battle cry “Remember Ludlow!” inspired advocates for labor and civil rights. By the 1970s, however, the fatalities in those coalfields felt like wounds from a distant past, and the massacre fell from political discourse and education curriculums.

And then the world changed back. The gains of labor began to be undone, and the factors that defined the conflict in Colorado are with us once again: class warfare, corporate monopoly, environmental ruin, the demand for workers’ justice, the influence of media and public opinion. One hundred years on, the Ludlow Massacre is a starkly contemporary tragedy.

* * *

By 8 am on April 20, mountain breezes were gusting up loose earth around the tents. A clear, mild morning and the ordinary busyness of the community belied an atmosphere of dread that had been lingering for days. Nerves tensed as a squad of Colorado state militiamen rode past the baseball diamond and washing lines, into the center of the settlement. The uniformed men demanded to search the camp. Union leaders refused. The military promised to return.

Strikers took this ultimatum as proof of a looming attack. After months of strain, the ground suddenly teemed with motion. Terrified noncombatants fled the colony for a protective row of hills to the north and west. “Everybody was in a hurry-flurry,” recalled the local postmistress, “getting their children out of the way.” Union men shouldering rifles deployed south and east across the flats, hoping to divert enemy fire away from the tents. On the other side of no-man’s land, the soldiers prepared for battle. Privates raced to fill sandbags. Leaving headquarters, Lt. Karl Linderfelt, the brutal leader of the militia’s most feared unit, packed a machine gun on a mule cart and headed off to the front lines.

The battle lasted for hours, but the events of this day stemmed from decades, even eons, of history. Seventy million years earlier, verdant organic matter was overtopped by earth and began the process of coalification. By the nineteenth century, surveyors in southern Colorado came across an arid territory devoid of rivers and sparsely treed. The land wasn’t well-suited for farming, but it abounded with resources. A single ten-mile zone, one engineer reckoned, contained enough coal to power 2,000 locomotives for a century.

“Fossil fuels and the energy they contained,” writes Thomas Andrews in Killing for Coal: America’s Deadliest Labor War, “transformed environments, refashioned everyday life, and deepened divisions of wealth and status.” Coal attracted railroads, steelworks, downtown business districts and monopoly capital. The Rockefeller family became majority owners of Colorado Fuel & Iron, the largest employer in the state. The laborers there were spectacularly diverse; twenty-four languages were spoken in the coalfields. African-Americans, Mexicans, Asians, Britons, Germans, Poles, Italians, Slavs, Swedes—all worked in close proximity. Many sojourned for a short stay and then returned home. Louis Tikas, from Crete, stayed and became a leader of the United Mine Workers, in charge of running affairs at the Ludlow colony.

No one knows who fired first. But by midmorning, it was war. Finding shelter in creek beds, foxholes and railroad cuts, the strikers sniped at the soldiers with hunting rifles and shotguns. Many of the union men had combat experience from European conflicts; maneuvering expertly, they sought to outflank the enemy position. State troopers were fewer at first, with less training and discipline, yet they dominated the battlefield. “The militia might have been outnumbered,” writes Scott Martelle in Blood Passion: The Ludlow Massacre and Class War in the American West, “but they were not outgunned.” Their machine guns fired thousands of rounds over the course of the day.

A soldier was shot in the neck and bled out. A striker “cried and cried” after being hit in the temple. A young man watching the battle had the top half of his skull blown off. An 11-year-old boy hiding in one of the tents fell dead with a bullet lodged in his brain. Wounded men and animals lay twisted across the field.

Militia reinforcements arrived throughout the afternoon. The strikers gradually fell back under the heightened assault by hundreds of soldiers. By 7 pm, the army pushed into Ludlow itself. The first tent began to blister and burn just as the sun was setting.

* * *

For decades, the Colorado Fuel & Iron Company had practiced every kind of industrial extortion or tyranny: overpriced company stores, lax safety standards, patriarchal social control, importation of scabs, exacerbation of ethnic rivalries. A coal miner in the district was three times more likely to be killed on the job than the average American laborer. Workers lived in company-owned hovels, which is why, when the work stoppage began, the UMW provided families with tents. Near a tiny railroad depot, miles from any town, Ludlow was the largest in a topography of camps that altogether housed more than 10,000 strikers.

A variety of grievances drove the workers toward open revolt, but the protest was fundamentally about the right to join a union. In April 1914, John D. Rockefeller Jr. sanctimoniously told Congress that his family’s commitment to the “open shop”—a capitalist euphemism for a nonunion workplace—was a great American principle. Labor organizers believed the right to be protected and sustained by a union was worth dying for. Their enemies were ready to kill to prevent it.

Even before the battle, the Colorado strike was among the deadliest industrial conflicts in US history. Since its beginning in September 1913, nearly twenty people had been murdered. Scuffles between workers and the corporation had drawn state militiamen to the coalfields. The soldiers had originally come to preserve the peace, but as the months passed, volunteers were largely replaced by a corps of mine guards, pit bosses and mercenaries, who showed open enmity toward the strikers. Recurrent gunfire inspired many families to entrench. Some dug pits under the floorboards of their tents. Beneath one of the largest structures, there was a deep bunker meant to serve as a maternity ward for the settlement’s pregnant women.

As night fell on the 20th, the soldiers rioted amid the flames. The men, a military investigation would find, “had passed out of their officers’ control; had ceased to be an army and had become a mob.” They looted dresses and suits, bedding, jewelry, bicycles, silverware. Meanwhile, they systematically burned the tents, dousing the fabric with coal oil before tossing matches on the pyre.

With the fires spreading, women and children still in the camp fled from shelter to shelter. Many congregated in the bunker turned maternity ward. Terrified of the marauding militia, they remained even as the tent above them became engulfed in flames. They coughed in the smoke, and their prayers quickened as the fire extracted the oxygen from their hiding place and the floorboards above them grew too hot to touch.

During the strike months, no one had done more than Tikas, the union leader, to forestall violence. He was a “power for good,” acquaintances would recall, a “very quiet man.” Working to secure amity until the first gunshots made peace impossible, he had spent the entire day of the battle rushing between the tents, shepherding dozens to safety.

When the soldiers arrived in the evening, Tikas asked permission to continue searching for survivors. In response, Lieutenant Linderfelt smashed his Springfield rifle over the unarmed man’s skull so hard that he separated the stock from the barrel. His soldiers then murdered the union leader, putting three shots in his back and leaving him as he fell, face down in the sand. Three days would pass before the soldiers allowed Tikas’s body to be removed for interment.

On April 21, the morning after the battle, the sun rose over a scene of desolation. Smoke curled into the sky above a debris-filled ruin. Canvas and wood had burned away, leaving behind wracked iron bedsteads and cook stoves. Whiskey bottles littered the ground. Militiamen torched any structures that remained intact, refusing access to the Red Cross and firing without warning on passersby.

It was almost midday when rescue workers finally searched the maternity ward. Beneath the charred remains of the tent, they discovered the bodies of two young mothers and their eleven children, all of whom had suffocated.

* * *

Initial news of a “sharp fight between militia and strikers” spread quickly across Western newspapers. Within weeks, Americans were already speaking of the “Ludlow Massacre.” From the very first moments, no one doubted the enormity of the horror. “Worse than the order that sent the Light Brigade into the jaws of death,” The New York Times editorialized, “was the order that trained the machine guns of the State Militia of Colorado upon the strikers’ camp of Ludlow.”

Yet even while commentators shaped a narrative of massacre, miners were already declaring the need for vengeance. A defiant funeral procession for Tikas stretched for miles across the prairie. The UMW issued a call to arms, rousing more than 1,000 strikers into the field. Workers mounted “a miniature revolution,” in Upton Sinclair’s words, destroying mine property, sacking company towns and killing as many people as had been slain at Ludlow. Their forces were approaching Denver itself before the US Army arrived to restore order.

The outrage ignited protests in major cities across the nation. Demonstrators jammed Union Square in New York City. Socialists took the conflict directly to the richest men on the planet, picketing the Standard Oil Building on lower Broadway. Under the pressure, Rockefeller collapsed and took to his bed.

Radical revolutionists found even these efforts insufficient. “This is no time for theorizing, for fine-spun argument and phrases,” wrote Alexander Berkman in Mother Earth. “With machine guns trained upon the strikers, the best answer is—dynamite.” Disciples soon heeded this injunction. On July 4, 1914, three anarchists died after a bomb they were constructing—almost certainly to assassinate Rockefeller—prematurely detonated in their East Harlem tenement.

The Rockefellers would spend years working to efface the tarnish of Ludlow from the family reputation. They financed a massive public relations campaign and created new forms of managerial practice, offering workers important concessions (though not the crucial one of union membership). Such innovations, demanded by the nightmare of Colorado, would become the hallmarks of twentieth-century industrial relations.

In 1918, the UMW unveiled a monument to the fallen near the site of the battle. It took only a few decades for the shrine to outlast its milieu: the mining industry abandoned Colorado, working families were forced to move on, and the granite monolith positioned a half-mile off Interstate 25, south of Pueblo, remained as one of the few testaments to what had once been a landscape of epic struggle.

Observing from the vantage point of a half-century later, Howard Zinn saw two ways of understanding Ludlow. “If it is read narrowly, as an incident in the history of the trade union movement and the coal industry,” he wrote, “then it is an angry splotch in the past, fading rapidly amidst new events.” A second, more expansive view, he believed, revealed the true significance of the events of 1914: “If it is read as a commentary on a larger question—the relationship of government to corporate power and of both to movements of social protest—then we are dealing with the present.”

The export of manufacturing jobs abroad has produced an undoing of memory. Today, the nation is divided by the kind of severe income disparities last seen during the Gilded Age, and yet the traditions of labor militancy and resistance to corporate ferocity that flowered in the era of heavy industry have been largely forgotten by both workers and employers. But Ludlow is the terminus of capitalism’s regressive path. If our future is shaped by the further degradation of labor rights, there can only be more massacres and new monuments.