The first ascent of the couloir was made on 22 May 1963, by Tom Hornbein and his partner, Willi Unsoeld, who were with the 1963 U.S.A. expedition attempting to reach the Everest summit from the Nepalese southern side by two routes. The majority of expedition members used the same route climbed ten years earlier by Tenzing Norgay and Edmund Hillary. This entailed negotiating the Western Cwm and the flank of Lhotse to the South Col, then up the southeast ridge to the peak.