This dissertation argues for the importance of works of leftist literary criticism, fiction, and poetry in our understanding of the cultural history of American modernism. Despite the scientific Marxist tendencies apparent in the critical debates that were conducted in the New Masses and at the 1935 American Writers' Congress, the leftist fiction of the decade reflects a critical Marxist stance, focused on alienation and the possibilities of formulating narrative strategies to overcome the distortions of ideology. Novels deployed a form of Lukacsian ideological critique, I argue, insofar as they engaged the stereotypes of high literary culture, as well as mass and popular culture, with historical materialism. This strategy is apparent in John Steinbeck's California labor novels, Nathanael West's surreal apocalyptic novels, and in Richard Wright's Thirties fiction, as well as in the lesser-known works of Robert Cantwell and Agnes Smedley. These works reveal a lineage of critical Marxism, engaging the dialectic of identity and ideology, a productive tension between subjective and objective forms of knowledge. The dialectic of ideology and identity explores human subjectivity in-itself and for-itself, both as a knowable object of rational inquiry as a radically unknowable experiential process. The latter prospect dovetailed with the nationalist paradigm of the American self, a figure of autonomous self-fashioning and reinvention that is central to the American novel tradition. While some novels enclose one aspect of the dialectic into the other, explaining away the ideological commitments of characters as symptoms of their psychological pathologies, for instance, as Steinbeck does, or on the other hand, underestimating the real effects of identity, as Wright does at his most ideological, the best works sustained the contradictions between these two discursive modes, "tarrying with the negative," to use the Hegelian phrase. The continued relevance of these works of literary leftism resides in their critical power, confronting and deconstructing the encroaching patterns of mass culture and gesturing beyond our categories of knowledge, not hubristically but warily.