A semiotic and cultural anthropological interrogation of popular North American superhero narratives, such as those of Superman, Spider-Man, and Batman, provides insight into how media's messages influence the culture's ethical values. Since emerging in the late 1930s, the superhero has become a pervasive figure in North American popular culture. As an extension of ideas presented by Friedrich Nietzsche, Joseph Campbell, and Umberto Eco, this dissertation argues that superhero tales must be regarded as modern mythology. It follows that people observe and learn social norms of justice from such narratives, since these ideals are intrinsic to the tales. In investigating the superhero's role as a contemporary figure of myth, this project focuses primarily on three areas: an account of the history of the superhero from 1938 to present; an examination of the cultural functions of contemporary superhero narratives; and, an interrogation of vigilantism, responsibility, and justice in these narratives and how those concerns further relate to ideologies and practices in North American culture.