Colorado coal miners — “colliers” — begin a strike in late 1913, seeking union recognition, 8 hour workdays, payment for all work, and the right to shop at non-company stores. The mining companies respond by evicting strikers from their company homes. They hire militias and call on the National Guard to break the strikes. On this day in 1914, armed with machine guns, they attack and burn a tent village of striking colliers and their families in Ludlow, at the base of the Sangre de Cristo Mountains. At least 21 people — mostly women and children — are killed.

Violent conflict spreads to mines across the state. 75 people die, in all, before Federal troops disarm all parties. The strikes end in December 1914 with no demands met and striking colliers replaced. 332 strikers are indicted for murder.