The American Puritan layman Samuel Sewall (d. 1730) is perhaps best known as a diarist and as a repentant judge in the Salem witchcraft trials. But he was also the author of Phaenomena quaedam apocalyptica (first edition 1697), a work which argued that the New Jerusalem would arise in Mexico City. Sewall’s unusual millennial doctrine may seem undeserving of study, for no other American Puritan thought that the New Jerusalem would first appear in Mexico City or anywhere else in New Spain. Yet when properly contextualized, the Mexican millennium is worth investigating for two reasons. First, it accentuates what the American Puritan millenarian mainstream, best exemplified by John Cotton, Increase Mather, and Cotton Mather, believed about the coming kingdom. Second, the Mexican millennium, like the mainstream position, challenges the academic claim that American Puritan millenarians characteristically believed that they were destined to inaugurate the millennial kingdom in New England.