Over 7.5 million individuals migrated to the United States from 1820 to 1870, amounting to more than the entire population of the U.S. in 1810.
Individuals migrated from northern and western European countries, with the largest concentrations coming from Ireland and Germany. This wave of immigration transformed the primarily Anglo-Saxon Protestant and British makeup of Europeans in the United States, igniting hostility toward the mostly Catholic German and Irish migrants.
Poor living conditions and the devastation of the potato famine in Ireland in 1845 sparked an onslaught of immigration, leading to approximately 4.5 million Irish migrating to the East Coast between 1820 and 1930. Irish laborers faced tremendous discrimination and worked at the lowest rungs of the occupational ladder. At the same time, however, the large number of Irish living in the United States helped them to mobilize for political and social influence. In contrast to most Irish migrants, German migrants were wealthier and sought out farmland and work in the Midwest. Overall, this wave of migration in the nineteenth century helped establish a foundation for future ethnically diverse migrations to the U.S.