From 1820 to 1850, the largest group of immigrants came to the United States from Ireland.
Between 1820 and 1860 a wide majority of immigrants came from northern and western Europe. The potato famine in Ireland which took place from 1845 to 1847 brought large numbers to the United States. Furthermote, the unsuccessful 1848 Revolution in Germany gave way to a considerable emigration to the United States.