According to the 2010 U.S. Census, America’s most populous ancestry groups were Germans (16.4%), African American (12.2%), and Irish (11.8%).
The most massive wave of Germans came to the United States through the middle of the nineteenth century, avoiding civilian crises and high unemployment rate. Nowadays, most German-Americans live in the non-coastal states, with the largest number in Maricopa County (Arizona).
Most African Americans are the descendants of slaves from Sub-Saharan Africa.
The great starvation of the 1840s triggered a mass emigration from Ireland. Within the 1820s and the 1920s, approximately 4.6 million Irish migrated to the U.S., many of them resided in big cities like New York City, Boston, Chicago, San Francisco, and Philadelphia.
The map below highlighted the national origin claimed by American citizens in each U.S. county.