This dissertation examines the visual aesthetics of popular American animated cartoons. For most of the twentieth century, the making of these films was mechanized and standardized to allow for high-volume production: thousands of drawings were inked and painted onto individual transparent celluloid sheets (called "cels") and then photographed in succession, a labor-intensive process that was divided across scores of artists and technicians, most of them anonymous. In order to understand how the industrial mode of production influenced the medium’s visual style, this dissertation regards each frame of a given animated cartoon as a historical document in its own right. What emerges is an original account of an art formed on the assembly line. The four chapters each provide a distinct perspective on the art, labor, and technology of cel animation. Drawing on the montage practices of Sergei Eisenstein and Walter Benjamin, the first chapter offers a model for understanding the historical and theoretical significance of the part (or, in this case, the frame) in relationship to the work of art as a whole. The second chapter focuses on cel animation's photographic basis, which has long been overlooked in film theory. Thinking of each of a film's frames as the photographic documentation of a singular instant in time reveals the labor that went into the film's production, a revelation that, in turn, imbues the cartoon with new aesthetic power. The third chapter uncovers moments of abstract painting—those frames in which a famous cartoon character is blurred or distorted beyond recognition—in order to rethink the possibilities of anonymous artistry, while the fourth explores the stylistic and economic shifts catalyzed by the introduction of xerographic technology (the Xerox machine) to the cel animation process. Ultimately, this dissertation argues that the method of frame-by-frame analysis constitutes its own form of aesthetic experience.