In the 1870s, the united Kingdom of Italy brought together nearly the whole Italian peninsula under a single flag, and the United States left behind a civil war and strengthened the country and its institutions. This dissertation is an account of the relations between the United States and Italy from 1871 to 1920. This era witnessed numerous important incidents like the mass Italian immigration to America beginning in the 1880s, military service and the problem of naturalization, the lynchings of Italian immigrants particularly in the southern United States, anarchism in both countries, Italian colonialist activities in North Africa, the beginning of American overseas expansion, and World War I. By analyzing both countries’ laws, political circumstances, internal affairs and ideological developments, the dissertation aspires to explore the aspects that shaped Italian and American foreign relations. While emphasizing these features, it seeks to clarify the fact that the main issue which both countries focused on was national greatness.