The role of private organizations and think tanks in the United States have been well documented. The Council on Foreign Relations in particular has been much discussed—less so, the Carnegie Endowment for International Peace. This article seeks to fill that gap by exploring its influence on American public opinion during World War II. Based upon archival research, the essay examines the background of the key members of the Endowment, their outlook and the impact their work had in shaping US attitudes. Using Gramsci's notion of an ‘historic bloc’ wedded to the insights of the ‘corporatist’ school of American foreign relations, the conclusion reached is that the organization—along with other key bodies situated at the interface between the private and public spheres—played a not inconsiderable part in educating Americans for internationalism before the end of the war and the onset of the Cold War two years later.