In the new location, struck by the sad conditions of immigrants, he joined the trade union movement. In 1904 he settled in New York City, where he studied briefly at Columbia University and took part in the meetings of a radical cultural club on 5th Avenue with socialists, anarchists and intellectuals.
In 1906 he started a co-operation with Carlo Tresca on the socialist journal, La plebe, and began renouncing his religious commitment. In 1908 he joined the Federazione Socialista Italiana and his first poem (in Italian) appeared in the May Day edition of Il proletario, the Italian-language newspaper of the Industrial Workers of the World (IWW).
In 1909 he started an Italian-language radical journal, La rivista rossa and continued to participate as a member of Il proletario's editorial committee. Two years later he assumed editorship of Il proletario and began writing in English.