John Hugh MacLennan was born to Dr.Samuel MacLennan, a physician, and Katherine MacQuarrie in Glace Bay; he had an older sister named Frances. His father was a stern Calvinist; his mother, creative, warm and dreamy. Hugh inherited traits from both. In 1913 they went to London where Samuel took courses for a medical specialty. When they returned to Canada, they settled briefly in Sydney, before moving permanently to Halifax where they experienced the Explosion in Dec. 1917, which Hugh later wrote about in his first published novel, Barometer Rising. He became good at sports, winning the men's N.S. double tennis championship in 1927. Both Frances and Hugh were pushed hard in their schooling by their father, especially in the Classics. Frances had no interest in these subjects, but Hugh did well in them, first at Dalhousie University, winning a Rhodes Scholarship to Oxford. He worked incredibly hard there but only reached second-class. In his 4th year, he spent more and more time on tennis and writing poetry, which was not accepted by the publishers to whom he sent it.
While in Europe he traveled to Italy, Greece, Switzerland, France and Germany. While sailing home in 1932, he met his future wife, Dorothy Duncan. His father was not pleased with her American background and insisted that he not marry before becoming independent. Since he was refused a job at two Canadian universities and had a scholarship for Princeton University, he completed his Ph.D.Oxyrhynchus:An Economic and Social Study, about the decline of a Roman colony in Egypt.
He wrote two novels during those years, one set in Europe, the other in the USA. but they were never published. It was his wife, whom he married in 1936, who persuaded him to set his work in Canada, the country he knew best. He had begun teaching at Lower Canada College in Montreal. She told him, "Nobody's going to understand Canada until she evolves a literature of her own, and you're the fellow to start bringing Canadian novels up to date." Until then there had been no real tradition of Canadian literature, and MacLennan set out to define Canada for Canadians through a national novel.Barometer Rising, his novel about the social class structure of Nova Scotia and the Halifax Explosion of 1917, was published in 1941.