A number of recent stories document the Trump administration’s continually escalating commitment to fulfilling the president’s disturbing campaign rhetoric regarding Mexican “illegals”:

CNN reports that the Department of Homeland Security has hired two anti-immigration activists who worked for groups founded by “a retired Michigan ophthalmologist who has openly embraced eugenics, the science of improving the genetic quality of the human population by encouraging selective breeding.” (Can you imagine a nation of selectively bred Michigan opthamologists?)

The Daily Beast’s Betsy Woodruff examines attorney general Jeff Sessions’ commitment to aggressive felony prosecution of undocumented immigrants charged with what would have been previously considered minor offenses. “The things they want us to do are so horrifying,” one federal prosecutor tells Woodruff, adding, “It’s fucking horrifying.”

The Washington Post documents internal Homeland Security plans to increase detention capacity by tens of thousands of beds, hire “hundreds” more agents, and deputize local police with immigration “enforcement authority.”

It adds up to a commitment to treat every undocumented immigrant—including those who are gainfully employed, have no criminal record, and have established themselves in their communities—as threats to the national interest who must be addressed with quasi-military urgency.

In light of this crackdown’s status as the only policy goal actually being pursued successfully by our white nationalist administration, it may be worth revisiting the reason we have so many “illegal” immigrants of Latin American origins in the first place—namely, a 1965 tweak to an immigration bill, backed by openly white supremacist senators such as Strom Thurmond, that was expressly intended to keep Latinos from achieving legal citizenship for no reason other than they weren’t white.

The law in question was the Hart-Celler Act, which I wrote about for Slate in 2015, and the tweak in question was a change that exponentially reduced the number of legal immigration slots available to countries in the Western Hemisphere. This reduction mostly affected Mexico: Before the law was passed, up to 50,000 Mexicans entered the U.S. each year as legal permanent residents while hundreds of thousands more entered on temporary work permits. This status quo was deeply upsetting to a bloc of conservative senators such as South Carolina’s Thurmond, a famous segregationist, and West Virginia’s Robert Byrd, who at that point had not yet fully renounced his past KKK membership. As I wrote (passage altered slightly for clarity):

South Carolina Republican Strom Thurmond argued that the imperative “to preserve one’s identity and the identity of one’s nation” justified restrictionist policies that favored Western Europeans because they could more easily assimilate into the existing (white) culture. These opponents furthermore added that uncapped Western Hemisphere immigration was itself a looming threat to the United States’ identity and stability. “The day is not far off when the population explosion in Latin American countries will exert great pressures upon those people to emigrate to the United States,” said West Virginia Democrat Robert Byrd.

The Thurmond-Byrd bloc was open about preferring European immigrants to others. Here’s a complaint another senator, North Carolina’s Sam Ervin, made at the time:

The people of Ethiopia have the same right to come to the United States under this bill as the people from England, the people of France, the people of Germany, the people of Holland. With all due respect to Ethiopia, I don’t know of any contributions that Ethiopia has made to the making of America.

That quote isn’t about Latino immigrants per se, but it gives you an unvarnished sense of the attitude held by those who wanted to restrict Latino immigration. They weren’t making an argument about public safety or economics—they were simply irritated by the idea of immigrants who weren’t white. (And, for the record, the evidence indicates that undocumented immigrants constitute an overall benefit to the economy and don’t present a disproportionate crime risk.)

To placate these white nationalist senators, the number of legal entry slots available to Mexico (and other Latin American countries) was slashed drastically. But the economic demand and geographic proximity that already pulled so many Mexicans into the U.S. did not abate. And voilà: Hundreds of thousands of people who had been entering the U.S. legally for years (and whose ancestral roots to North American land went a lot further back than those of many white Americans) were suddenly “illegal” if they crossed an imaginary line on a map in order to work.

And now, here we are!