As northern factories grew, employers could not hire enough workers. In response, European immigration to the North soared. One and a half million came to the United States in the 1840s alone. The Irish were the paradigm. By 1845, 220,000 had already come in a decade not half over, and the second half saw 550,000 Irish refugees arrive in the United States, fleeing British oppression and a famine that killed millions.
