What follows is taken from the United Mine Workers website.
The Ludlow Massacre
The date April 20, 1914 will forever be a day of infamy for American workers. On that day, 19 innocent men, women and children were killed in the Ludlow Massacre. The coal miners in Colorado and other western states had been trying to join the UMWA for many years. They were bitterly opposed by the coal operators, led by the Colorado Fuel and Iron Company.
Upon striking, the miners and their families had been evicted from their company-owned houses and had set up a tent colony on public property. The massacre occurred in a carefully planned attack on the tent colony by Colorado militiamen, coal company guards, and thugs hired as private detectives and strike breakers. They shot and burned to death 18 striking miners and their families and one company man. Four women and 11 small children died holding each other under burning tents. Later investigations revealed that kerosene had intentionally been poured on the tents to set them ablaze. The miners had dug foxholes in the tents so the women and children could avoid the bullets that randomly were shot through the tent colony by company thugs. The women and children were found huddled together at the bottoms of their tents. . . .
The rest of the article can be found at: http://www.umwa.org/?q=content/ludlow-massacre
A thorough listing and discussion of commemorative events is available at: https://www.facebook.com/Ludlow100