Eric R. Simonson, leader of the Mallory and Irvine Research Expedition, has been a mountain guide since 1973. He is a founding partner of International Mountain Guides and Mount Rainier Alpine Guides, based in Ashford, Washington. Since 1970, Simonson has summited Mount Rainier 260 times and participated in or led more than seventy high-altitude expeditions on seven continents, including twenty in both the Alaska Range and the Himalayas. He has summited Mount McKinley sixteen times and climbed Mount Everest seven times, summiting in 1991. Simonson is one of the most experienced and successful expedition leaders in the world. He lives in Ashford, Washington.