From Vox: How the Immigration and Nationality Act transformed America, in one chart

A 2015 article that provides an alternative theory about why things changed back in the 1960s.

- Click here for the article. 

The INA replaced the overtly racist immigration regime of the mid-20th century, which fully banned immigration from Asia or Africa and set strict national quotas designed to limit immigration from southern and eastern Europe. The quotas were based on the ethnic balance of the 1890 census — when, in the opinion of the Congress of the time, the United States was still a properly "white" country and wasn't in danger of being overrun with Italians and Jews.

The Immigration and Nationality Act replaced this with the legal immigration system we still use today. There's a flat cap on how many immigrants per country can immigrate each year, but individual immigrants aren't approved or denied based on where they come from. Instead, they're admitted largely through family members in the US; temporary work permits for specific employers; or refugee status or asylum (along with assorted other, smaller categories).

You can see the results in the chart above, which displays the number and origins of immigrants — naturalized citizens, legal immigrants, and unauthorized immigrants — living in the United States during the 1960 census (before the INA) and during each decade after.

In 1960, immigrants to the US were overwhelmingly European. Furthermore — at least partly because so few eastern and southern Europeans had been allowed into the country under the quota system — Jewish and Italian Americans had largely assimilated into the US, and were considered white in a way they weren't in the 1920s. But really, there were relatively few immigrants in the US at all.

The INA opened the door to millions of immigrants. The percentage of the US population that is foreign-born is almost as large today as it was during the peak of US immigration at the turn of the 20th century — when unlimited numbers of immigrants from Europe could come to the United States, but when there were only half as many people living in the US as there are today.