Striking began in late summer 1913, organized by the United Mine Workers of America (UMWA) against the Rockefeller-owned Colorado Fuel and Iron (CF&I) after years of deadly working conditions and low pay.

In retaliation, armed miners attacked dozens of mines and other targets over the next ten days, killing strikebreakers, destroying property, and engaging in several skirmishes with the National Guard along a 225-mile (362 km) front from Trinidad to Louisville, north of Denver.

Contemporaneous accounts suggest the Blair Mountain strikers feared Baldwin-Felts would utilize a gun-equipped truck on their number, erroneously believing that the Death Special had been present at the Ludlow Massacre.

However, local CF&I fuel manager E. H. Weitzel retained Pinkerton detectives in the Southern Colorado coalfields to monitor the collective organizing of miners in the region.

"During this initial stage of the strike, Governor Ammons met several times with Welborn, Osgood, and David W. Brown—representing CF&I, Victor-American, and the Rocky Mountain Fuel Company respectively.

The escalating situation caused Governor Elias Ammons to call in the Colorado National Guard in October 1913, but after six months all but two companies were withdrawn for financial reasons.

Balwin-Felts detectives George Belcher and Walker Belk had killed UMWA organizer Gerald Liappiat in Trinidad on 16 August 1913, five weeks before the strikes began.

[39] Dealers in Walsenburg and Pueblo also sold explosives to both sides of the conflict, though the investigating congressional committee noted they did "not believe a majority of the people of Colorado indorse [sic] such actions.

[23] A Colorado and Southern (C&S) route that connected the Front Range and passed near the Ludlow Colony began to be used as a firing position to harass strikers on 8 October 1913, resulting in no immediate casualties.

Fearing a military response, an armed group of Greek strikers were sent by John Lawson to prevent troops from arriving in the area by the C&S train, and they fired with little effect on it as it passed through.

[18]: 125–126  Lieutenant Linderfelt, one of the first deputized into the militia, then led a group of 20 militiamen to hold a section house along the railway a half-mile south of Ludlow when at 3 pm they came under fire from strikers in elevated positions on the ridges.

[22]: 250 Baldwin-Felts detective George Belcher was killed by Italian striker Louis Zancanelli in Trinidad on 22 November in what the National Guard's official report deemed an assassination.

[39]: 30 Due to the influence of the Colorado National Guard and Greek Union leaders, such as Louis Tikas in Ludlow Colony, the strike had become relatively peaceful by the beginning of 1914.

The official report by the National Guard detachment commander at Aguilar to General Chase on 18 January denied the claim, as did a telegram to Governor Ammons sent personally from Linderfelt.

[46] On 8 March 1914 the body of a strikebreaker, Neil Smith, was found on the train tracks near the Forbes tent colony, located near the then-emptied Rocky Mountain Fuel Company town of the same name, an incident that occurred as a congressional committee was touring the area.

[39] In retaliation, the Guard destroyed the colony on 10 March, burning it to the ground while most inhabitants were away and arresting all 16 men living in the tents, an action that indirectly resulted in the deaths of two newborn children.

[47] The withdrawal of the majority of the National Guard had left only two companies of troops in the strike area, with these soldiers spread across several encampments at Berwind, Ludlow, and Cedar Hill.

Major Patrick Hamrock, the Irish-born leader of the "Rocky Mountain Sharpshooters" and a veteran of the Wounded Knee Massacre, persuaded Tikas to meet at the Ludlow train stop.

[i][18]: 213 [34] Sensing the militia's intent to act that day after seeing machine guns placed above the colony and choosing to disobey Tikas, strikers took cover in hastily constructed fire positions.

[18]: 214–215 [53] Accounts of who fired the first shot differ, but fighting began or escalated after the militia at Ludlow detonated warning charges to notify Linderfelt's troops stationed at Berwind Canyon and another detachment at Cedar Hill.

John O. Ferris, Episcopalian minister of Trinity Church in Trinidad and St. Mary's in Aguilar, and a small group of others from the nearby communities were among the few permitted into the still-smoldering tent colony.

[5]: 189 [59] These events led the sheriff of Las Animas County to send a telegram to Ammons, declaring that he had been militarily defeated by the miners and requested federal intervention.

The following day, John McLennan, the president of UMWA District 15 when the strike was declared, was arrested by militia at the Ludlow train stop on his way from Denver to Trinidad.

[18]: 259–260 [21]: 160  With the return of open hostilities came an increased formalization of military operations on both sides, with the union and militia forces each publishing communiqués reporting casualties and advances while diminishing the claimed successes of their opponents.

[22]: 278–279 [5]: 222–223  Clara Ruth Mozzor—a social worker who would later become the first female Assistant Attorney General of Colorado—wrote for International Socialist Review in 1914 that "waste and ruin, death and misery were the harvest of this war that was waged on helpless people.

[22]: 282  Pro-union publications lamented the failure to secure immediate significant structural change in the relationship between miners and the CF&I and criticized the Guard and militia's response and actions at Ludlow.

[79] Major Patrick Hamrock and Lieutenant Karl Linderfelt were tried in separate courts-martial from the rest of the National Guard and militia involved in the suppression of the strike, as they faced additional charges of assault with a deadly weapon in relation to the deaths of strikers in custody at Ludlow, including Tikas.

[101] Leftist historian Howard Zinn said Ludlow and the strike were "the culminating act of perhaps the most violent struggle between corporate power and laboring men in American history.

Following significant damage from vandalism in 2003, a celebration of the monument's restoration occurred on 5 June 2005 with roughly 400 people, including UMWA President Cecil Roberts, in attendance.

[108] On 19 April 2013, Colorado governor John Hickenlooper signed an executive order creating the Ludlow Centennial Commemoration Commission in preparation for the hundredth anniversary of the Massacre a year later.