In his 1952 McGill University yearbook, Dr. Harold Don Allen M.S. ’66 wrote, “The secret of success is constancy of purpose,” forecasting a lifelong commitment to teaching and inspiring others. Indeed, he taught generations of math students and future teachers, instilling a sense of wonder in bright young people about the beauty of numbers and cryptograms, and wrote the weekly science and math column for children, “How and Why by Uncle Don,” which ran in over 200 issues of the Montreal newspaper, Le Messager Verdun. Don was awarded masters degrees from Santa Clara 1966 and Rutgers University in 1968, and his doctorate in mathematics education, a source of enormous pride for him throughout his life, was conferred on him by Rutgers in 1977. Growing up Montreal, Don spent his summers in a remote, lakeside cottage in Sainte-Anne-des-Lacs, during which time he fostered a love of nature and animals, becoming a lifelong vegetarian in his teens (although he’d turn a blind eye to the use of a few eggs in his wife, Fran’s magnificently moist chocolate brownies). He and Fran had four children and, later, four grandchildren. They travelled extensively and simply, always with a camera in hand, across Canada and the U.S., and to Europe, the Middle East, and Asia. Don particularly loved the Canadian North and the people who lived there, appreciating their closeness to nature and the hard work and constancy of purpose required to live in balance with it. When he died on July 11, 2020, his children found consolation and no coincidence that their father had chosen to see his prime-number 89th birthday and await a prime-number day in a prime-number month to pass peacefully away.