On this date in 1596, the Inquisition sent nine Jewish converts to Christianity to the stake in Mexico City for Judaizing — a cruel fate offering a window into a secret history of New World settlement. When Spain expelled its Jews (and subsequently its Muslims), those who did not flee had to convert. Conversions at swordpoint being of suspect sincerity, the Inquisition spent much of the following centuries hunting Conversos — so-called “New Christians” — who secretly preserved their outlawed faiths. For some crypto-Jews, the New World held an appeal akin to that which would draw later generations of northern...