Between 1917 and 1920, more than twenty states passed criminal-syndicalism laws making membership in a union that advocated "industrial change by force" a felony — statutes aimed at the IWW and used against communists and strike organizers for two decades. California alone prosecuted over 500 people and imprisoned 128 at San Quentin and Folsom, from Charlotte Anita Whitney to the entire leadership of the 1930s agricultural strikes; the Imperial Valley and Sacramento conspiracy trials filled this database with farm-labor prisoners.

Idaho, Washington, Oregon, and Kansas ran parallel campaigns, and Oklahoma's statute jailed Communist organizers into the 1930s. Only in DeJonge v. Oregon (1937) and the slow repeal era did the laws recede — after establishing, for a generation of American workers, that the union card itself could be the indictment.