The Whistler Valley was formed by the pass between the headwaters of the Green River and the upper-middle reaches of the Cheakamus. It is flanked by glaciated mountains on both sides; the Garibaldi Ranges on the side that contains the ski mountains, and a group of ranges with no collective name but which are part of the larger Pacific Rangesand are essentially fore-ranges of the Pemberton Ice field. Although there are a few other routes through the maze of mountains between the basin of the Lillooet River just east, the Cheakamus-Green divide is the lowest and most direct and naturally was the main trading route of the Squamish and Lil'wat First Nations long before the arrival of Europeans. One Lil'wat legend of the Great Flood says that before the deluge, the people lived at Green Lake.
The first British survey by the Royal Navy took place in the 1860s. These surveyors named the mountain London Mountain because of the heavy fog and cloud typically gathering around the mountain, but the area informally acquired the name "Whistler" due to the call of the hoary marmot. In the late 19th century, a trail was cut through the valley, linking Lillooet via Pemberton with Burrard Inlet via a pass from Squamish to the Seymour River. The trail was completed in 1877, but because of the difficult and unforgiving terrain, it was only used once for its intended purpose, which was to drive cattle. The area began to attract trappers and prospectors (such as John Millar and Henry Horstman) who established small camps in the area in the early 20th century. The area began to gain recognition with the arrival of Myrtle and Alex Philip, who in 1914 purchased 10 acres (4.0 ha) of land on Alta Lake and established the Rainbow Lodge. The Philips had relocated from Maine to Vancouver in 1910, and had heard rumours of the natural beauty of the area from Pemberton pioneer John Millar. After an exploratory journey, the couple was convinced. Rainbow Lodge and other railway-dependent
