社会主義者鎮圧法
Rosenberg was forced to emigrate from Germany in 1880 under the pressure of the Anti-Socialist Laws of 1878, landing in America. Rosenberg resumed life as a language teacher in Boston for the Berlitz School of Languages. He joined the fledgling Socialist Labor Party of America (SLP) around this same time. Rosenberg subsequently moved to Chicago, where he served as editor of a succession of politically oriented newspapers, including "Die Fackel" (Sunday edition of the "Chicagoer Arbeiter-Zeitung," 1881-1884), the SLP's official organ, "Der Sozialist" (1885–1889), "Der Tramp" (New York, 1888), and "Vorwärts," (New York City, from 1892).