In 1937 Bates, with Bradford Washburn, made the first ascent of Mount Lucania in Yukon, which was then the highest unclimbed mountain in North America. It was also one of the most remote and inaccessible and had been declared virtually impregnable. The pair enlisted the aid of the pilot Robert Reeve to fly them to the mountain, but when they landed on the Walsh Glacier the aeroplane sank into the unexpectedly soft snow. After they had spent five days digging it out Reeve departed, warning Bates and Washburn that he would not be able to return to collect them as planned and that they would have to walk back to civilization. The pair climbed Mount Lucania, and the nearby Mount Steele, and were then faced with a trek through wilderness to Burwash Landing, without maps. They abandoned some of their food to save weight, expecting to restock at a cache left behind by an earlier expedition. However, the cache had been plundered by bears, and Bates and Washburn survived on mushrooms and squirrels during the trek out. Flooded rivers forced them to detour many miles out of their way, and they had eventually walked an estimated 156 miles by the time they reached Burwash Landing, 32 days after arriving on the glacier. The two men lost around twenty pounds each during the walk out.