A fire and a gun battle between the Colorado National Guard and striking coal miners led to 17 deaths in the Ludlow Massacre.

The Colorado National Guard consists of the Colorado Army National Guard and Colorado Air National Guard, forming the state of Colorado's component to the United States National Guard. Founded in 1860, the Colorado National Guard falls under the Colorado Department of Military and Veterans Affairs.

The Ludlow Massacre was a mass killing perpetrated by anti-striker militia during the Colorado Coalfield War. Soldiers from the Colorado National Guard and private guards employed by Colorado Fuel and Iron Company (CF&I) attacked a tent colony of roughly 1,200 striking coal miners and their families in Ludlow, Colorado, on April 20, 1914. Approximately 21 people were killed, primarily miners' wives and children. John D. Rockefeller Jr. was a part-owner of CF&I who had recently appeared before a United States congressional hearing on the strikes, and he was widely blamed for having orchestrated the massacre.