Gros Ventre Slide

The 1925 Gros Ventre Slide was the largest rockslide in recorded U.S. history. The event occurred in the Gros Ventre, about 6 and a half miles east of Kelly, WY. The slide was so large it dammed the river, creating a new lake, and caused a flood that destroyed the town of Kelly. You can still see the scar of the massive slide today, on the road to Red Rock Ranch.

The drive to Red Rock Ranch from Jackson Hole takes around 45 minutes but the gorgeous scenery along the way makes it seem much quicker. Don’t go too fast, though. There are points of interest along the way that you may not want to miss.

Things like the Gros Ventre Slide.

The Largest Rockslide in U.S. History

On June 23, 1925, the north face of Sheep Mountain broke free in a half-mile wide landslide.

The estimated 50,000,000 cubic yards of debris hurtled down the mountain at 50 mph. The slide’s momentum and debris was so great that, upon reaching the valley, it flowed up the opposite slope for another 300 feet.

Gros Ventre Slide and Lower Slide Lake
Lower Slide Lake

The slide effectively dammed the flow of the Gros Ventre River, forming the five-mile long Lower Slide Lake that still exists today. A Forest Ranger and others nearby heard the roar and marveled at the giant cloud of dust caused by the slide.

Downstream, Kelly residents took to higher ground, concerned that the natural dam could fail at any moment, flooding the town. Geologists and engineers were called in to survey the dam. They gave it their stamp of approval, calling it safe and permanent.

A Deadly Flood

Not everyone was as convinced as the experts, however and, after the harsh winter of 1926-27, their fears were born out.

On May 18, 1927 heavy spring runoff caused a portion of the natural dam to fail, sending a huge wall of water rushing downstream for at least 25 miles. Luckily, the residents of Kelly had some warning, so only six people perished in the deluge.

The town, itself, was not so lucky. Only the school, church, and parsonage were left standing. More than 40 families were left destitute, relying on the kindness of their neighbors in nearby Grovont, WY. Eventually the town received federal aid and those who remained began rebuilding.

Viewing Gros Ventre Slide

Gros Ventre Geological Site

You can easily see the Gros Ventre Slide during your drive to Red Rock Ranch. In fact, the Gros Ventre Geological Site parking area is only 9 miles from our Wyoming dude ranch.

The parking area for the site sits directly below the slide, providing a clear view of the scar. Several informational panels detail the event through historical accounts and pictures.

You’ll also find the Gros Ventre Slide Interpretive Trail trailhead here. The 0.6 mile loop trail is easy for all skill levels and provides excellent views of the slide and Lower Slide Lake.

There are no facilities on site but there are some bathrooms nearby. Learn more about this fascinating natural attraction at