by Don H. Doyle

In the summer of 1861, an American diplomat in Turin, Italy, looked out the window of the U.S. legation to see hundreds of young men forming a sprawling line. Some wore red shirts, emblematic of the Garibaldini who, during their campaign in southern Italy, were known for pointing one finger in the air and shouting l'Italia Unità! (Italy United!).

Now they wanted to volunteer to take up arms for l'America Unità! Meanwhile, immigrants already in the United States responded to the call to arms in extraordinary numbers. In 1860, about 13% of the U.S. population was born overseas—roughly what it is today.

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Source: http://time.com/