Mining was dangerous and difficult work. Colliers (coalworkers) in Colorado were at constant risk for explosion, suffocation, and collapsing mine walls. In 1912, the death rate in Colorado's mines was 7 per 1,000 employees, compared to a national rate of 3. The high death was due in part to Colorado's unique geology, but also due to poor enforcement of safety regulations. In 1914, the United States House Committee on Mines and Mining reported that "Colorado has good mining laws and such that ought to afford protection to the miners as to safety in the mine if they were enforced, yet in this State the percentage of fatalities is larger than any other, showing there is undoubtedly something wrong in reference to the management of its coal mines." Miners were generally paid according to tonnage of coal produced, while so-called "dead work", such as shoring up unstable roofs, was often unpaid.
Colliers had little opportunity to air their grievances. Many colliers resided in company towns, in which all land, real estate, and amenities were owned by the mine operator, and which were expressly designed to inculcate loyalty and squelch dissent.. Welfare Capitalists believed that raising colliers’ standard of living, while keeping it under company management, could placate anger and unrest among the workers. Company towns indeed brought tangible improvements to the lives of many colliers and their families, including larger houses, better medical care, and broader access to education. However, ownership of the towns provided companies considerable control over all aspects of workers' lives, and this power was not always used to augment public welfare. What more, miners who angered or spoke out against the company were liable to find themselves and their families summarily evicted from their homes.
Frustrated by working conditions which they felt were unsafe and unjust, colliers increasingly turned to unionism. Nationwide, organized mines boasted 40 percent fewer fatalities than nonunion mines. Colorado miners had repeatedly attempted to unionize since the state's first strike in 1883 but coal companies often hired strike breakers to prevent or break strikes. CF&I's management mixed immigrants of different nationalities in the mines, a practice which discouraged communication that might lead to organization.
Despite attempts to suppress union activity, secret organizing by the UMWA continued in the years leading up to 1913. Eventually, the union presented a list of seven demands on behalf of the miners, including recognition of the union, increase in wages, enforcement of the 8 hour work day, payment for “dead work,” the right to use any store and choose their boarding houses and doctors, and strict enforcement of Colorado’s mining laws.
The major coal companies rejected the demands and in September 1913, the UMWA called a strike. Those who went on strike were promptly evicted from their company homes, and they moved to tent villages prepared by the UMWA. The tents were built on wood platforms and furnished with cast iron stoves on land leased by the union in preparation for a strike.
The company hired the Baldwin-Felts Detective Agency to protect the new workers and harass the strikers. Baldwin-Felts had a reputation for aggressive strike breaking. Agents shone searchlights on the tent villages at night and fired bullets into the tents at random, occasionally killing and maiming people. They used an improvised armored car, mounted with a machine gun the union called the "Death Special," to patrol the camp's perimeters. The steel-covered car was built in the CF&I plant in Pueblo, Colorado from the chassis of a large touring sedan. Frequent sniper attacks on the tent colonies drove the miners to dig pits beneath the tents where they and their families could be better protected.
The strikers persevered until the spring of 1914. On the morning of April 20, the day after Easter was celebrated by the many Greek immigrants at Ludlow, three Guardsmen appeared at the camp ordering the release of a man they claimed was being held against his will. While this meeting was progressing, two companies of militia installed a machine gun on a ridge near the camp and took a position along a rail route about half a mile south of Ludlow. The miners, fearing for the safety of their families, set out to flank the militia positions. A firefight soon broke out.
The fighting raged for the entire day. By 7:00 p.m., the camp was in flames, and the militia descended on it and began to search and loot the camp. During the battle, four women and eleven children had been hiding in a pit beneath one tent, where they were trapped when the tent above them was set on fire. Two of the women and all of the children suffocated. These deaths became a rallying cry for the UMWA, who called the incident the "Ludlow Massacre."
In response to the Ludlow massacre, the leaders of organized labor in Colorado issued a call to arms, urging union members to acquire "all the arms and ammunition legally available," and a large-scale guerrilla war ensued, lasting ten days. In Trinidad, Colorado, UMWA officials openly distributed arms and ammunition to strikers at union headquarters. 700 to 1,000 strikers "attacked mine after mine, driving off or killing the guards and setting fire to the buildings."
The UMWA finally ran out of money, and called off the strike on December 10, 1914.
In the end, the strikers failed to obtain their demands, the union did not obtain recognition, and many striking workers were replaced by new workers. Over 400 strikers were arrested, 332 of whom were indicted for murder. Only one man, John Lawson, leader of the strike, was convicted of murder, and that verdict was eventually overturned by the Colorado Supreme Court. Twenty-two National Guardsmen, including 10 officers, were court martialed. All were acquitted, except Lt. Linderfelt, who was found guilty of assault for his attack on Louis Tikas. However, he was given only a light reprimand.
Although the UMWA failed to win recognition by the company, the strike had a lasting impact both on conditions at the Colorado mines and on labor relations nationally.
A United States Commission on Industrial Relations (CIR) conducted hearings in Washington, collecting information and taking testimony from all the people involved, including John D. Rockefeller. The commission's report suggested many reforms sought by the unions, and provided support for bills establishing a national eight-hour work day and a ban on child labor.