The more liberal immigration policies of 1965 still form the scaffolding of the United States’ legal immigration system, ushering in — if unintentionally — an America that grows less white every year. For years now, Asians, Africans and Hispanics have accounted for an expanding proportion of the country’s visas.

But first came 1924, when the people in charge spoke openly of ranking immigrants of certain origins above others.

That was the year Congress passed an immigration overhaul that set strict quotas designed to encourage immigrants from Western Europe, block all but a few from Southern and Eastern Europe and bar altogether those from Asia. Overall immigration levels were slashed. The racial theories at play in the legislation, wrote the immigration historian Roger Daniels, would later become the first draft of “the official ideology of Nazi Germany.”

There were some familiar refrains in the 1924 immigration debate. Cheap immigrant labor had depressed wages, the restrictionists said. Immigrants had seized jobs from Americans, they said. But it was also heavy on racist rhetoric aimed at preserving what eugenicists and social theorists of the time called the “Nordic” race that, in their telling, had originally settled the United States.

The bill’s authors had been avid readers of the 1916 book “The Passing of the Great Race,” in which the eugenicist Madison Grant warned that the country was in danger of a “replacement of a higher type by a lower type here in America unless the native American uses his superior intelligence to protect himself and his children from competition with intrusive peoples drained from the lowest races of Eastern Europe.”

Under the 1924 law, the number of visas given to each country could not exceed annual quotas based on the number of people from that country who were living in the United States as of the 1890 census, before the flow of new Americans had begun to tilt away from Western European countries.