Thomas Pynchon’s novel Mason & Dixon suggests that when Charles Mason and Jeremiah Dixon journeyed westward in order to draw a line between Maryland, Pennsylvania, and Delaware, they did more than merely settle a border dispute. Indeed, in Pynchon’s revisiting of American history, Mason and Dixon’s westward journey functions as an ecological allegory for the line the explorers draw “inflict[s] upon [the Earth] a long, perfect scar” and separates (or, rather, seeks to separate) humanity from nature. However, this separation between humanity and the nonhuman species inhabiting the planet cannot be consistently maintained, as the novel demonstrates. This incongruity between mankind’s desire to control the planet and nature’s chaotic design emerges as the driving force in the novel’s (eco)gothic aspirations: talking dogs who have “learn’d to act as human as possible” confuse their human counterparts and their neat binary divisions of the world, while automatons that simulate animals develop consciousnesses of their own and come to haunt humans for eradicating their natural brothers and sisters. On the other hand, the human characters repeatedly confront the animal within, not only in the wilderness but also in the “civilized” spaces of human settlements, such as when Dixon “feels like a predatory Animal, —as if this Town were … his Hunting-Ground” or “become[s] a Werewolf, or … some New World Creature without a name.” As this chapter will demonstrate, Mason & Dixon thus suggests that the violent establishment of a man-made world, which has left behind “a clear sign of Human Presence upon the Planet,” brought forth various specters that would haunt humanity “unto the year 1900, and beyond.”