The 1959 Hebgen Lake earthquake (also known as the 1959 Yellowstone earthquake) occurred in the western United States on August 17 at 11:37 pm (MST) in southwestern Montana. The earthquake measured 7.2 on the moment magnitude scale, caused a huge landslide, resulted in over 28 fatalities and left $11 million (equivalent to $102 million in 2021) in damage. The slide blocked the flow of the Madison River, resulting in the creation of Quake Lake. Significant effects of the earthquake were also felt in nearby Idaho and Wyoming, and lesser effects as far away as Puerto Rico and Hawaii.