The Civil War offered a huge opening. Hundreds of thousands of immigrants volunteered for military service on both sides. Not surprisingly, the Union Army, about one-fourth of whose personnel came from abroad, benefited from immigrant support more than the Confederacy. [...] Confederates looked askance at the Union's polyglot ranks, and for decades afterwards Civil War Decoration Day holidays offered embittered former Confederates occasions to characterize their side as "American" and to impugn the Union Army as "made up largely of foreigners and blacks fighting for pay."

— The History of White People by Nell Irvin Painter (Page 202)