This was the birthplace of Provincetown’s one home-grown national hero: Rear Admiral Donald Baxter MacMillan (1874-1970), an intrepid and imaginative Arctic explorer, anthropologist, geographer and naturalist who lived for many years at 473 Commercial Street, not far away. Childhood was cruel for MacMillan. When he was 9 years old, his father, Capt. Neil MacMillan, and the entire crew of the schooner Abbie Brown perished in a gale off Newfoundland. That left Sarah Gardner MacMillan, whose father had been a shipbuilder, with five children to care for alone. Already in frail health, she died when “Donny Baxter” was 12 years old. For a time, the boy was cared for by one or two other seafaring families in town, but was finally sent to Freeport, Me., to live with an older sister who had married.