1880–1930 -- During this peak period of immigration, interrupted only by World War I, more than 27 million immigrants, many from southern and eastern Europe, come to the United States. More than 4 million come from Italy and 9 percent of the total population of Norway emigrates to the United States. Massive migration of eastern European (especially Russian) Jews occurs in the early 1880s, due to anti-Jewish persecution and massacres in Europe. (Library of Congress)