This volume argues that Jack London's Martin Eden and Henry Adams' The Education of Henry Adams are two of the first works in American literature to embody the motif of existentialism. The development of the existential dilemma in each work will be supported through references to earlier European existentialist writers, with Nietzsche as a focal point. The 19th century fin de siècle was a time of tremendous change, both materially and philosophically. The dawn of the last century was a time of great wealth and imperialistic expansion for Western civilization, but also a time in which the seeds were sown for later military conflict; the enormity of which the world had never witnessed before. From the vantage point of the post-World War years, the materialism of the fin de siècle was a decorative façade that concealed from view the underlying reality of the human abyss. The outbreak of the First World War changed all of that, and the two works examined here anticipated that change. Henry James described the underlying reality of the fin de siècle when he remarked: "To have to take it all now for what the treacherous years were all the while making for and meaning is too tragic for any words." Henry Adams and Jack London mirror this sentiment in their respective works by depicting the philosophical turbulence of the 19th century fin de siècle.