Congress envisioned a white, Protestant and culturally homogeneous America when it declared in 1790 that only “free white persons, who have, or shall migrate into the United States” were eligible to become naturalized citizens. The calculus of racism underwent swift revision when waves of culturally diverse immigrants from the far corners of Europe changed the face of the country.

As the historian Matthew Frye Jacobson shows in his immigrant history “Whiteness of a Different Color,” the surge of newcomers engendered a national panic and led Americans to adopt a more restrictive, politicized view of how whiteness was to be allocated. Journalists, politicians, social scientists and immigration officials embraced the habit, separating ostensibly white Europeans into “races.”