During the decades separating the two world wars, Americans often defined themselves politically in reference to the Soviet Union. For most individuals, this meant eyeing Moscow with suspicion or hostility. A significant number of reformers and radicals, however, drew inspiration from the October Revolution. They viewed the Soviet Union as a vast, daring experiment that wedded scientific planning with ideals of equality in all areas of human endeavor: economics, statecraft, nation-building, gender relations, and so on. The most devoted enthusiasts joined the American Communist Party (CP), which, since its founding in 1919, committed itself to establishing a Soviet-style “dictatorship of the proletariat” in the United States. Hundreds of thousands of individuals belonged to the party, affiliated “front-groups,” and allied organizations, for greater or lesser periods of time, between the 1920s and 1940s. Always plagued by high turnover within its ranks, the CP never came close to achieving its ultimate goal. Still, it exerted a profound influence on the American left by transmitting ideas and policies formulated in Moscow to the United States.