An 1850 census showed that 961,719 Ireland-born people were living in the United States. The numbers of Irish immigrants per year in the United States are as follow: 92,484 in 1846, 196,224 in 1847, 173,744 in 1848, 204,771 in 1849, and 206,041 in 1850. (From http://www.spartacus.schoolnet.co.uk/USAEireland.htm, Irish Immigration) These overwhelming numbers had an enormous effect on American society. Once the Irish arrived in America, most found jobs as unskilled workers for the mines, railroads, or canals.
When the American Civil War broke out, about 210,000 Ireland-born Americans joined the war, mostly with the Union. Though most Irish-Americans felt the threat of losing their jobs if slaves were to be freed, the majority supported the Union. Because of the large Irish population in large cities like New York City, Boston, and Chicago, Irish-Americans were able to gain political jobs. Between 1820 and 1920, 4,400,000 Irish people had come to the United States, a number only surpassed by Germany and Mexico.