Mallory participated in the initial 1921 Mount Everest expedition, organised and financed by the Mount Everest Committee, that explored routes up to Everest's North Col. The expedition produced the first accurate maps of the region around the mountain, as Mallory, his climbing partner Guy Bullock, and E. O. Wheeler of the Survey of India explored in depth several approaches to its peak. Under Mallory's leadership, and with the assistance of around a dozen Sherpas, the group climbed several lower peaks near Everest. His party were almost certainly the first Westerners to view the Western Cwm at the foot of the Lhotse face, as well as charting the course of the Rongbuk Glacier up to the base of the North Face. After circling the mountain from the south side, his party finally discovered the East Rongbuk Glacier—the highway to the summit now used by nearly all climbers on the Tibetan side of the mountain. By climbing up to the saddle of the North Ridge (the North Col), they spied a route to the summit via the North-East Ridge over the obstacle of the Second Step.