He showed up on Long Island in the summer of 1919 with a polo mallet in one hand and a business card reading, “George Gordon Moore, Capitalist,” in the other. London had been his financial playground before the war, but the war had bled England dry.

Forty-five at the time, Moore knew there was wealth to be mined on Long Island’s North Shore. With its country estates and pristine oceanfront, it was a paradise for socialites, celebrities, and well-heeled entrepreneurs in search of glamour and the good life. Long Island was one of those places, as F. Scott Fitzgerald wrote in The Great Gatsby, where “people played polo and were rich together.” And that’s where Moore—my grandfather, and a likely model for Fitzgerald’s hero—met the man who would become the novel’s antagonist, Tom Buchanan.