The word immigration comes from the Latin immigratio, meaning “to go into,” and entered English in the 1600s.

Its opposite is emigration, with the two terms simply describing the same move from different directions, looking at the country someone enters versus the country they leave, so the same person is an immigrant to the new country and an emigrant from the old one.

People have been moving to new places for tens of thousands of years.

Modern humans left Africa about 60,000 to 70,000 years ago, reached Australia more than 50,000 years ago, and arrived in the Americas around 15,000 years ago.

Europe has seen continuous movement throughout its history, with modern humans arriving there about 45,000 years ago, followed over time by farmers, Romans, Goths, and Vikings, and after 1945 by immigration from former colonies along with guest worker programs.

For most of its early history, the United States had open borders, with few federal laws restricting entry for its first century.

That changed with the Chinese Exclusion Act of 1882, the country’s first major immigration restriction.

The best periods for immigration tended to come when the country needed labor, as in the 1840s and 1850s when millions of Irish and German immigrants arrived, and from the 1880s to 1920 when Ellis Island welcomed waves of Europeans.

The worst periods came when the country turned against particular groups.

The Chinese Exclusion Act banned many Chinese immigrants, more than a million people of Mexican descent were forced out in the 1930s, and 120,000 Japanese Americans were placed in internment camps during World War II.

Treatment varied sharply by origin: Northern and Western Europeans faced few barriers and general acceptance, Chinese immigrants faced the harshest treatment, Mexicans were often blamed for economic troubles and deported en masse, and Southern and Eastern Europeans were viewed as inferior and restricted under the 1924 quota laws.

Immigration has been a political flashpoint for a long time.

It first appeared in a party platform in the 19th century and by the 1850s the anti-immigrant Know Nothing party had become a major political force.

In 2016, Donald Trump made immigration his signature issue, and by 2024 he was calling it the single most important issue facing the country.

Access to public benefits today depends heavily on immigration status.

Undocumented immigrants are ineligible for most welfare programs, though they can still receive emergency medical care, public education for their children, and short-term disaster relief.

Legal immigrants have broader access: green card holders, refugees, and asylees can qualify for programs like food stamps and Medicaid, though most must wait five years, while refugees and asylees are typically exempt from that waiting period.

Temporary visa holders, DACA recipients, and TPS holders are largely barred from federal benefits, and the “Public Charge” rule can even hurt a legal immigrant’s chances of getting a green card if they’ve used certain benefits.

Immigrants also contribute substantially in taxes.

In 2022, undocumented immigrants alone paid about $97 billion in federal, state, and local taxes, with a large share going toward Social Security and Medicare even though they generally can’t draw on those programs themselves.

All immigrants combined paid around $383 billion in taxes that year, and over time immigrants can pay more in taxes per person than the average U.S.-born citizen.

The 14th Amendment also plays a major role in who is born a citizen.

Without it, an estimated 255,000 children born in the U.S. each year would not receive citizenship, a number that could grow to about 4.8 million by 2045 and 5.4 million by 2075.