The 1959 Hebgen Lake earthquake also known as the 1959 Yellowstone earthquake occurred on August 17 at 11:37 pm (MST) in southwestern Montana, United States. The earthquake measured 7.3 – 7.5 on the Richter magnitude scale, and caused a huge landslide that caused over 28 fatalities and left $11 million (1959 US$, $88.7 million 2014 US$) in damage. The slide blocked the flow of the Madison River resulting in the creation of Quake Lake.