The New Social Studies movement was an effort by social scientists to reform US social studies/history curriculum at all levels during the 1960s and early 1970s. In the end, more than 50 different projects attempting to revitalise social studies were developed. Many of the projects focused on inquiry-based teaching practices and curriculum. Considered to be the most controversial of the projects developed was Man: A Course of Study (MACOS) which sought to restructure social studies instruction by emphasising social science empiricism. The purpose of this historical analysis was to explore the curricular, ideological and financial obstacles that contributed to the eventual demise of the MACOS project. The author proposes that federally funded MACOS challenged the "history-as-national-progress" paradigm of the early to mid-twentieth century. This precipitated an ideological "conflict" that called into question the nature and purpose of social studies education. The study of MACOS's demise provides an insightful lesson on how the reception of curriculum innovation is subject to changing sociopolitical ideologies and the practicalities of instructional implementation. (Contains 83 footnotes.)