West Ridge Forerunner: Thomas F. Hornbein and the Development of the Maytag Oxygen Mask for the 1963 American Mount Everest Expedition.

Those with an interest in the history of mountaineering are aware of the visionary achievement of the first ascent of the West Ridge of Everest-and first traverse of the mountain-by Tom Hornbein and Willi Unsoeld during the 1963 American Mount Everest expedition led by Norman Dyrunfurth. In many respects, this climb defined Hornbein (1930-2023) in the eyes of the international mountaineering community. One aspect of his career in high altitude mountaineering that also reflected his professional interests has received scant attention. This largely overlooked contribution was that of the design and development, in the years and months leading up to the American expedition to Everest, of a more capable and comfortable mask for use with an open-circuit supplemental oxygen system. The primary intent of this paper was to relate the story of what came to be known as the Maytag mask, but the authors also provide a brief backdrop to Hornbein's life and times to give perspective to his endeavors in the valleys as well as on the peaks.