The school curriculum in the United States historically has been shaped by tradition, changing social and economic conditions, professional considerations, and political pressures. Through the nineteenth century curriculum forms earlier transplanted from Europe gradually modified to accommodate social and political realities in the United States. Curriculum reforms during the progressive era responded to general changes caused by industrialization and urbanization and also to specific educational conditions. Curriculum reforms in the 1920s and 1930s reflected a coalescence of a consciousness of curriculum development as a systematic, pragmatic, and participatory process. Curriculum reform during the 1940s and 1950s was characterized by a maturation of considerations pertaining to the needs of the student in tandem with the nature of society and of subject matter as curriculum sources and by a conservative backlash against four decades of progressive curriculum reforms. During the 1960s and 1970s curriculum reforms responded to perceived and real national crises – from the threat of Soviet space and military superiority, to social and political movements of the 1960s, to economic recession in the 1970s. During the 1980s and 1990s and into the first two decades of the twenty-first century curriculum reforms sought to harness the school curriculum in service of bolstering the international economic competitiveness of the US economy. Throughout myriad reform campaigns, the subject-centred curriculum remained a constant.