This dissertation complicates the narrative of American environmental thought by revealing how many Americans held anxieties about the dynamic relationship between human nature, human identity and the environment. The most extreme manifestation of these fears were Wild Men: human beings who, as a result of their exposure to the transformative power of nature, became covered in hair, endowed with great physical prowess, and stripped of speech. Wild Men, and the discourse on human and wild nature they embodied, shaped and were shaped by discourses of race, gender and class. In communities across the nation, Americans inscribed this fantastic image upon actual human beings on the margins of American society such as Native Americans, escaped slaves, vagrants, and the mentally ill, seeing them not as humans but as Wild Men. The results were violent attempts at redeeming those seen as Wild People from the wilderness that had transformed them. This project begins by arguing that a Texas community attempted to capture the Wild People of the Navidad because they embodied its concerns regarding the vulnerability of civilization during the Texas Revolution. Next, it traces the genealogy of the Wild Man figure in Native American, African American and Europe cultures. The following chapter explores the exhibition and examination of a Wild Woman and Wild Man by medical authorities in Cincinnati and Louisville in 1856 and 1878. Chapter four uses theories of power and legal liminality to understand the care and cruelty that the Wild Man of the Chilhowee experienced in post-bellum Tennessee. In the fifth chapter, I explore the life of Joseph Israel/Lucy Ann Lobdell to understand how wild behavior became pathologized in the last decades of the century. The sixth chapter explains the rise of the Wild Man in American culture at large from the 1840s to the popularization of evolutionary theory following the Civil War. Finally, the seventh chapter illustrates how, by the early twentieth century, the Wild Man image had fractured in response to changes in medical, biological and juridical knowledge and practice, creating figures in American and Canadian culture as diverse as Tarzan and Sasquatch.