Not hard to find. Just drive into the park from the St Mary entrance for several miles and you will see the signs for the Wild Goose Island overlook. Drive about 100 yards further to the next big pullout and the shooting location is just off the highway.
This a sunrise photo of Wild Goose Island on St Mary Lake in Glacier National Park. There are several overlooks from Going To The Sun highway and I took this shot from a small clearing about a hundred yards north of the most used overlook where so many of these shots are taken.