Jack Bonnell Dennis was born on October 13, 1931, in Elizabeth, New Jersey, to Wolcott Dennis and Nereide Bonnell. His father was from Seattle and was employed at the Air Reduction Company in New Jersey. His duties there included “boiling air,” an oxygen extraction process where air is cooled to a liquid form, then gradually heated to “boil off” the nitrogen, leaving pure liquid oxygen. Dennis’s mother grew up in Elizabeth, New Jersey, and became a teacher. When Jack was one year old, the family moved to Darien, Connecticut.