William Siri
William E. Siri (January 2, 1919 – August 24, 2004) was an American biophysicist, mountaineer and environmentalist. He was born in Audubon, New Jersey, and attended Audubon High School. Siri earned a physics degree from the University of Chicago in 1942.
He joined Lawrence Berkeley National Laboratory in 1943 and worked there for his entire career. During World War II, he contributed to the Manhattan Project from 1943 to 1945. After the war, his research focused on nuclear medicine, using radioisotopes to study red blood cells. He edited the Handbook of Radioactivity and Tracer Methodology, published in 1948 for the Army Air Corps. Siri became interested in how red blood cells respond to stress, such as high altitude, and worked with John H. Lawrence on this work.
In 1954, Siri led a ten‑man Sierra Club expedition that attempted Makalu, but bad weather forced them back at 23,000 feet. This was the first American expedition to the Himalayas. In 1957 he took part in a joint American-British Antarctic expedition studying the effects of extreme cold on blood. He was deputy leader and scientific coordinator of the successful 1963 American Everest expedition, where five Americans and a Sherpa reached the summit; Siri did not summit. He later described Everest as the highest place on Earth and noted the mountain’s enduring allure.
Siri served on the Sierra Club board from 1956 to 1974 and was its president from 1964 to 1966. He won the Sierra Club’s Francis P. Farquhar Mountaineering Award in 1979. He died of pneumonia in Berkeley, California, after suffering from Alzheimer's disease for about a decade.
This page was last edited on 2 February 2026, at 22:02 (CET).