This chapter examines the World War One period in which the federal, state, and local governments in the United States, in addition to non-state actors, created one of the most severe eras of political repression in United States history. The Espionage Act, the Sedition Act, changes to immigration law at the federal level, and state criminal syndicalism laws served as the legal basis for repression. The Partido Liberal Mexicano (PLM), Industrial Workers of the World (IWW), and other anarchists took different paths in this era. Some faced lengthy prison sentences, some went underground, while others crossed international borders to flee repression and continue organizing. This chapter examines the repression of radical movements and organizing continuities that sustained the movement into the 1920s.