Parts of the route had been closed at the end of last month because of flooding caused by heavy rainfall, the National Park Service said in a statement, and had reopened on June 30.
Downpours can contribute to landslides, as saturation can weaken rocks on slopes.
“With rainfall and flooding, rockfalls and washouts may occur, creating dangerous conditions,” according to a statement posted last month on the Glacier National Park’s Facebook page.
Since its construction in the late 1920s and early 1930s, Going-to-the-Sun Road has become one of the park’s most popular areas to visit, according to the Park Service. The route features views of glacier-carved peaks, alpine lakes and forests.
Fatal rockfalls involving visitors to Glacier National Park are rare, the Park Service said.
The most recent episode, in 2019, involved a 14-year-old girl from Utah who died after rocks hit the top of a vehicle she was in, shattering the windshield. Four other people in the car were injured, the service said.