During the past year, there’s been a lot of talk about “chain migration” coming out of Washington, D.C., in the national conversation about immigration. Much of this talk has been distinctly negative.

But where would we be without chain migration?

Here’s where we wouldn’t be — Baltimore, New York or anywhere else that large Jewish communities have gathered. And our fellow Americans of Italian, Irish, Polish, Chinese, German and Scotch-Irish descent wouldn’t have much of a presence either.

Chain migration describes the historical process by which most migrations occur. One or two pioneers move to an area of likely settlement. If they find opportunity, they write home and tell their relatives and friends. Slowly, these relatives start to join them, first in a trickle and gradually in larger numbers.

Historians and demographers labeled this widespread phenomenon “chain migration” back when the field of immigration studies took off in the 1960s, and have used it ever since.

Chain migration is responsible for the “family circles” and hometown societies that played an important role in Jewish social life late into the 20th century in Baltimore and other cities. If you go back into your family history, you probably will find your own ancestral stories of chain migration, though of course no one would call it that since the term has been used only by academics.

Until now. Recently, the term has been employed by those who would keep today’s immigrants from our shores.

Their fear has historical precedent. In the early 20th century, nativists railed against “dangerous immigrants” from “races … which have never assimilated and who are most alien to the great body of the people of the United States,” as Sen. Henry Cabot Lodge (R-Mass.) put it in 1909. Those races, he proclaimed, included “Italians, Russians, Poles, Hungarians, Greeks and Asiatics.” Non-Protestants were especially reviled, and not only Jews. In 1911, a popular anti-immigrant newspaper called Catholicism “the most dangerous power that threatens our government today.”

Such sentiments led Congress to pass legislation in the 1920s that drastically reduced immigration and imposed limits based on “national origin.” The legislation sought to exclude people of undesirable race and religion, with quotas favoring white Protestant northern Europeans while severely restricting southern and eastern Europeans (who were largely Catholic or Jewish and not considered white).

The quotas, along with new bureaucratic procedures making the immigration process much more difficult, had tragic consequences for Jews trying to escape Nazi Europe the following decade. Those who did manage to slip in through the quota system often were admitted because they had relatives in the United States.

In other words, chain migration saved their lives.

Congress ended this chapter of racial and religious exclusion with the Immigration and Nationality Act of 1965. Though we never returned to the days of uncapped immigration, the act set new criteria for who could move to the U.S. The concept of family reunification — which officials had used to help determine whom to admit under the old quotas — became enshrined in law as a major reason for admittance. Despite later tweaks, our current immigration policy stems largely from the 1965 law.

And what of the immigrant hordes who struck such fear into the hearts of critics such as Henry Cabot Lodge? Some of them did not assimilate. Again, if you go back into your family history, you might hear about the bubbie whose broken English led her to speak Yiddish all her life. Your great-great-grandparents might have been among the many who lived and worked in East Baltimore’s Jewish immigrant enclave and relied on their young children to help them deal with the outside world. Those children, of course, became fully American.

The same process has repeated with every generation of newcomers to arrive in the U.S. from around the globe. All of these immigrants made America what it is today.

And it all started with chain migration.

Dr. Deborah R. Weiner is co-author of “On Middle Ground: A History of the Jews of Baltimore,” to be published this spring by the Johns Hopkins University Press.