This work reconsiders the history of the Socialist Party of America during the Great Depression and the unaffiliated social-democratic movement developed by those who left the Socialist Party to join President Roosevelt’s New Deal coalition. The substance and implications of socialism’s revival in the 1930s have received insufficient attention, overshadowed by an emphasis on the character and impact of American communism. Viewed over multiple decades, socialists remained relevant in the labor movement. Their integration into the New Deal coalition confounds claims that American socialists were too rigid and programmatic in their beliefs to be effective political actors in the United States. Their shift from a revolutionary socialism to a pragmatic embrace of social democracy suggests that socialists were able to find an accommodation with both capitalism and with the Democratic Party. For much of the Depression, the Socialist Party was a vibrant political force on the American left, challenging the mainstream parties to address the economic crisis, creating a space in which women claimed leadership, and provided a cohort of skilled organizers for the labor movement. During the revival, women were central to the party’s successful organizing efforts, provided vital election support, publically debated the meanings of femininity and masculinity, and held important offices within the party. Socialists also built institutions. Highlander and Soviet House, two institutions that must be understood within their proper socialist contexts, developed out of the radicalism fostered by Reinhold Niebuhr at Union Theological Seminary. Radical young socialists, drawn to Reinhold Niebuhr’s pessimistic critique of capitalism, carried their belief that capitalism was in its terminal crisis into the SP’s Revolutionary Policy Committee. Their energy yielded impressive organization success for the labor movement. The continued intellectual coherence of socialists in the decades after the revival suggest that evolving socialist ideas survived within and at odds with the New Deal coalition. Far from abandoning socialism, those socialists who participated in the New Deal coalition maintained a distinctive set of ideas. The existence of a strong cohort of women in the Socialist Party’s revival runs contrary to scholars’ claims that women did not play a significant role in the Socialist Party after the early 1920s. Socialist women rebuilt socialist institutions during the Depression. They were central to the party’s successful organizing efforts; provided vital election support; debated the meanings of femininity and masculinity; and held offices within the party. Viewed from within the confines of parties and elections, the history of the socialist movement in the United States appears limited in its scope and importance. During the 1930s, socialists’ successful municipal projects were eclipsed by rising factionalism and the unrequited attraction of revolution. Socialists seemed much less interesting and their critiques less incisive and useful when mired in historical accounts that give primacy to factional feuds and electoral politics. This was not the entirety of the socialist experience in the 1930s. Socialists did fight amongst themselves and against communists, primarily with words but also with fists. They also served as productive forces and provided significant leadership within the labor movement. Throughout those decades, they continued to distinguish themselves from other trade unionists. Socialists retained their class-based critique of American society even as they softened their ideas about the remedies that they intended to employ to make that society more equitable.