Nearly 60 Years Ago, Wyoming Had a Massive 7.5 Earthquake
We're nearing the 60th anniversary of an earthquake so large it partially knocked a mountain down. It's known as the Hebgen Lake earthquake and it had the largest magnitude in the history of Wyoming.
It happened the night of August 17, 1959. According to the Wyoming State Geological Survey, it registered a 7.5 on the Richter scale. The Hebgen Lake earthquake Wikipedia page indicates it struck at 11:37 pm that night.
Technically, the epicenter of the quake was in southwestern Montana, but it devastated Yellowstone National Park causing a landslide. In total, 28 people lost their lives as a result of the Hebgen Lake earthquake.
The earthquake was so severe, it created a lake out of part of the Madison River (now known as Quake Lake).
According to Wikipedia, there were several major aftershocks after the main quake including a 6.5 on August 18, 1959. New geysers even appeared in Yellowstone National Park after this earthquake.
Earthquake Track and other websites show that the Hebgen Lake earthquake has now been reclassified as a 7.2, but the truth is it really doesn't matter. It was a killer and Wyoming has not seen a larger quake in the nearly 60 years that have followed.