NPR Fresh Air: Nearly 100 years ago, Congress passed a restrictive law that cut the overall number of immigrants coming to the United States and put severe limits on those who were let in.

Journalist Daniel Okrent says that the eugenics movement — a junk science that stemmed from the belief that certain races and ethnicities were morally and genetically superior to others — informed the Immigration Act of 1924, which restricted entrance to the U.S.

"Eugenics was used as a primary weapon in the effort to keep Southern and Eastern Europeans out of the country," Okrent says. "[The eugenics movement] made it a palatable act, because it was based on science or presumed science."

Okrent notes the 1924 law drastically cut the number of Jews, Italians, Greeks and Eastern Europeans that could enter the country. Even during World War II, when hundreds of thousands of people were displaced and dying, access remained limited. The limits remained in place until 1965, when the Immigration and Nationality Act ended immigration restrictions based on nationality, ethnicity and race.

Okrent sees echos of the 1924 act in President Trump's hard-line stance regarding immigration: "The [current] rhetoric of criminality, the attribution of criminality — not to individual criminals but to hundreds of thousands of people of various nationalities — that's very similar to the notion of moral deficiency that was hurled by the eugenicists at the Southern and Eastern Europeans of the 1910s and '20s."

Okrent's new book is The Guarded Gate.