Speculator Mine disaster Wikipedia
The Granite Mountain/Speculator Mine disaster of June 8, 1917, occurred as a result of a fire in a copper mine, and was the most deadly event in underground hard rock mining in United States history. Most men died of suffocation underground as the fire consumed their oxygen; a total of 168 miners were killed. The Butte, Montana copper mines were at full wartime production to support the US in the Great War.