The Columbia Broadcasting System (C.B.S.) emerged in the late 1920s as the only sustainable competitor to the National Broadcasting Company (NBC) in American network radio. But scholars know far less about C.B.S. than NBC because the C.B.S. corporation failed to retain, and make accessible to media historians, internal archival and documentary materials from its developmental era. This article examines the historical void created by America’s second network while offering two specific historical case studies to establish how the loss of C.B.S. materials continues to hinder knowledge about America’s second network, the American system of broadcasting, and the political economy of the commercial mass media in the United States.