This thesis follows debates about economic planning during the 1930s through the work of Lewis L. Lorwin; his organization, the National Economic Planning Association; and its journal, Plan Age, to recover a rich intellectual legacy. Economic historians have marginalized the economic planning movement, regarding it as an aberration and failure. Instead, the planners played a central role in many important transitions, including the shift from laissez faire to Keynesian economics, an essential ingredient in the U.S. ascendance to global power. Marxian class analysis is the method used to explore the contradictions of the economic planning movement, explain its successes and failures, and measure the extent and limits of its challenges to liberal economic and political theory, with special attention to the ways in which the movement simultaneously undermined and reinforced capitalism and imperialism. In the process new directions are suggest for contemporary critics and activists.