[ Sinclair / King Coal ]
This novel — a politically charged work (as most of Sinclair's novels were) about a Colorado coal miners' strike — has one (metaphorical) reference to Newfoundlands (Book 3, Section 1):
He was round-faced, like a full moon, and as jolly as Falstaff; when you got to know him better, you discovered that he was loyal as a Newfoundland dog.