In the early 20th century, the possible effect of large-scale immigration upon the labor market was the subject of spirited debate, including among labor advocates. Today, at least in progressive circles, even raising the question is nearly verboten.

A century ago, some progressives also raised legitimate concerns about the impact of mass immigration on national cohesion. The tensions between different national-origin groups in the United States noticeably deepened as World War I approached. Contrary to the reigning view that Germans were the object of unfounded prejudice and mistreatment while the Allies fought with the kaiser, historians have presented ample evidence that Germans in America openly displayed intemperate sympathy for the Fatherland.

In November 1915, the young Reinhold Niebuhr — a Lutheran pastor in Detroit, a son of German immigrants, and later a renowned liberal theologian — complained in a November 1915 letter to a mentor: “Among the ministers here at least and among many that I know of in other parts there is no real interest in the welfare of this country and no genuine American patriotism.” He continued, “Every aspect of German life and culture is glorified and practically every aspect of American life is ridiculed.”

Foreign conflicts echoed in American streets. In cities like Chicago, Polish immigrants sided with formally neutral America and vehemently opposed their German neighbors’ vociferous support for their ancestral homeland. Meanwhile, Irish immigrants and their American-born relatives sided with Germany and opposed America’s implicit support for Britain and the Allies. Not surprisingly, once America entered the war against Germany, such voices in support of the kaiser greatly diminished. But they did not disappear completely, nor did the sentiments behind them — evidence that, upon their arrival on these shores, immigrant identities did not immediately dissolve into a melting pot of Americanism.