Between the 1880s and 1920s, a broad coalition of American dissidents, which included rabble-rousing cartoonists, civil liberties lawyers, socialist detectives, union organizers, and revolutionary martyrs, forged a culture of popular radicalism that directly challenged an emergent corporate capitalism. Monopoly capitalists and their allies in govern-ment responded by expanding conspiracy laws and promoting conspiracy theories in an effort to destroy this anti-capitalist movement. The result was an escalating class conflict in which each side came to view the other as a criminal conspiracy. In this detailed cultural history, Michael Mark Cohen argues that a legal, ideological, and representational politics of conspiracy contributed to the formation of a genuinely revolutionary mass culture in the United States, starting with the 1886 Haymarket bombing. Drawing on a wealth of primary sources, The Conspiracy of Capital offers a new history of American radicalism and the alliance between the modern business corporation and national security state through a comprehensive reassessment of the role of conspiracy laws and conspiracy theories in American social movements.