Beginning in the 1830s and lasting up to the Civil War, immigrants from Ireland, Germany, and Scandinavia poured into the United States, comprising a wave of what came to be called "Old Immigrants." Several factors helped spur this increase in immigration in the decades leading to the Civil War. In Ireland, the Irish Potato Famine ravaged the country beginning in the 1840s. A fungus destroyed the potato crop, which was Ireland's staple crop. Thousands died during the famine and many more left the country, especially since new steam engines made travel more affordable. Poverty, land shortages, and political unrest also drove many immigrants to flee their countries, especially in Germany and Scandinavia. The combination of political freedom and economic opportunity attracted immigrants to the US. Women could work in domestic industries while men could find work in the emerging cities and factories. In addition, land proved plentiful in the West, and while many Irish immigrants settled in cities, Germans typically became farmers or brewers in the Midwest and West.
There were numerous sociopolitical effects of this new wave of immigration. New cultures and traditions emerged as German immigrants exposed their new homeland to traditions such as the Christmas tree and kindergarten. Especially in cities, the Irish became involved in politics, giving rise to political machines such as William "Boss" Tweed's Tammany Hall in New York. Nativist sentiments also increased as Americans reacted to the new immigrants. The "Know-Nothing" Party (later renamed the American Party) formed in the 1850s to oppose immigration, especially Catholic immigrants. Many Americans deeply distrusted Catholicism and Catholic immigrants, believing they were too influenced by the Pope. The temperance movement also increased during this time period, as many Americans associated both the Germans and the Irish with heavy drinking, which they believed ruined society and morality and broke apart families. Nativism continued to be a theme throughout US history and affected US immigration policy, as seen in the Chinese Exclusion Act in 1882 and the immigration quotas of the 1920s. These debates over immigration continue today, especially as immigration patterns shift and migrants from various parts of the world seek refuge, opportunity, or new lives in the US.