De Grasse was born in Bathurst, New Brunswick, and he trained to be a dentist. He married Annie McDonnell in 1904. Their daughter, Clementine Bell, was born in 1906. Annie died in 1909, probably in childbirth with another daughter, Olive. In 1910, Samuel was practicing dentistry and he and Clementine were living in Providence, Rhode Island along with his older sister (also named Clementine) and her 14-year-old son, Jerome Fauchy.