Which Immigrant Group Was The Largest During The Period From 1820 To 1920?

Which Immigrant Group Was The Largest During The Period From 1820 To 1920? Overview. From the 1820s to the 1840s, Germans and Irish were the two largest groups of immigrants to the United States. The Germans and Irish were frequently subjected to anti-foreign prejudice and discrimination. Where did most immigrants come from in the 1920s?