Harry Truman became a modern folk hero 45 years ago for his steadfast refusal to leave his lodge in the shadow of Mount St. Helens, even as experts warned that the volcano in southwestern Washington might erupt. Reporters covering the rumbling mountain in the spring of 1980 often turned their attention to Truman, describing the 83-year-old business owner and former bootlegger as gruff, stubborn, funny and, above all, fiercely independent. And those depictions were more or less accurate, said Dan Plute, a Clarkston Heights man who is Truman’s grandson-in-law. “A lot of people used the word crusty,” Plute said last...