Many Montanans in 1959 had lived through the Helena earthquake of 1935. Even if they weren’t in the capital city at the time, they could remember news of the destruction – more than $4 million in property damages and four people left dead. The earthquake of ‘35 was the worst natural disaster to hit the Treasure State since the Great Fire of 1910. And in 1949 Montanans endured even more misfortune with the loss of thirteen men and 4,500 acres to the Mann Gulch Fire along the upper Missouri River. Each of these disasters had resulted in tragedy and the Hebgen Lake earthquake of 1959 was no different.

At 11:37pm on August 17, 1959 an earthquake measuring between 7.3 and 7.5 struck in Madison Canyon, west of Yellowstone National Park. The earthquake lasted 30-40 seconds (with multiple aftershocks) and the shockwaves caused numerous seiches (standing waves) on Hebgen Lake, along with the worst landslides in the Northwestern United States since 1927.

The earthquake, aftershocks, and landslides caused parts of Hebgen Lake to rise as much as eight feet and created hurricane-force winds in the valley. Because it was summer and the location was in such close proximity to Yellowstone, campgrounds in the area were occupied with visitors, some of which were sleeping when the earthquake struck. Landslides swept people and property away, wind blew over car and trailers, and a seiche from Hebgen Lake flooded nearby campgrounds.

At Yellowstone, the earthquake caused new geysers and cracks to form and damaged the Old Faithful Inn, which had to be evacuated. The town of Ennis was evacuated as well due to concerns that Hebgen Lake would flood the area. (It was later discovered that a landslide blocked this from happening.)

Meanwhile, roads and highways around Hebgen Lake collapsed into the water. Fault scarps – some nearly 20 feet high – caused damage to other roads and structures. More roads still became blocked by landslides.

Evacuation and response to the disaster became difficult with roads cut off and the situation was exacerbated by the fact that telephone communications between Yellowstone and Bozeman had been severed.

Areas all over the state and beyond experienced the effects of the earthquake. Fatalities reached as far as Raynolds Pass in Idaho, where eight people were killed in a landslide, and minor effects were felt as far away as Puerto Rico, where the earthquake caused water in wells to drop .01 feet. A landslide which blocked the Madison River, caused the water to flood, creating a new lake which was later dubbed Quake Lake. Altogether, $11 million dollars in damage was done and upwards of 28 people were killed. A memorial service was held for those buried in the slide at Madison Canyon and a plaque was later hung in their honor, upon completion of the Quake Lake Visitors Center.