Cornthwaite was born in
Saint Helens, Oregon on April 28, 1917. His interest in acting began in his early teens, when he was forced to recite one line in a school play. He began his acting career in 1937, appearing in a college production of
Twelfth Night, while attending
Reed College in
Portland, Oregon. Cornthwaite began his time in the US Army Air Force as a radio-gunner in B-25 aircraft as part of the 12th Medium Bombardment Group in 1942. He then served as a radio operator and superintendent of the watch with the 79th Fighter Group from 1943-1944. This was followed by serving as a writer and broadcaster with the Mediterranean Allied Air Forces from 1944 until 1945. In this position he performed Public Relations duties in
Naples, Rome,
Corsica, and other locations in the Mediterranean area. While on Corsica, Cornthwaite worked on his first film which was for the Free French Air Force. He acted as a writer and sound engineer recording Capitaine
Eve Curie (daughter of
Marie and
Pierre Curie) of the Free French Air Force. He did the commentary in French and English. Cornthwaite also dubbed the voice of American Air Force General
Ira Eaker, who did not speak French. In 1951, Cornthwaite was cast in
Howard Hawks's production of
The Thing from Another World. His character, Dr. Carrington, the unofficial leader of an Arctic polar expedition, observes the nearby crash of an
unidentified flying object, and urges his military counterparts to communicate with the creature inside, even at the cost of their own lives. This performance eventually earned him entry into the "Science Fiction Hall of Fame" in 1993. Other notable films include
The War of the Worlds,
What Ever Happened to Baby Jane?,
Colossus: The Forbin Project and the
Joe Dante production of
Matinee, in which he shared screen time with fellow 1950s screen notables,
William Schallert and
Kevin McCarthy in the "film within a film", "MANT", a spoof of sci-fi films. Similarly, Cornthwaite appeared as Dr. Carrington opposite Ken Tobey (again as Hendry) in a spoof titled
Attack of the B Movie Monster, shot in 1984. Expanded and retitled
The Naked Monster, it was released on DVD in 2005 by Anthem Pictures. ==Stage and television work==