In a bid to free up jobs after the onset of the Great Depression, hundreds of thousands of people were deported from the United States to Mexico. The majority were American citizens.
The Great Depression hit the United States hard in 1929. And when the going gets tough, the tough get racist. Herbert Hoover was a notoriously anti-immigrant president (one of many, it seems), but the depression gave him the excuse he needed to become even worse. He could claim that he was freeing up jobs for Americans by taking a hard line against the many legal Mexican migrants in the country, and by encouraging local action rather than doing it all at a federal level he kept his hands legally clean.
In some places migration to Mexico was “encouraged” through fear and intimidation; in others such as Los Angeles it was paramilitary raids and throwing people onto buses or trains and dumping them far across the border. Imagine something like the Bisbee deportation, but hundreds of times larger and running for seven years.
Here’s the real kicker: people of Mexican heritage had been in the United States for a very long time. California, Utah, Nevada, New Mexico, Texas, and parts of other states, were territories of Mexico up until the mid-18th century. (Well, large parts were inhabited by native American peoples, but officially the whole area was Mexican.) Legal Mexican migrants in the area had local-born children who were birthright citizens of the United States. The Mexican Repatriation did not distinguish between legal migrants, illegal migrants, and actual American citizens: all were exiled.
It’s difficult to find exact numbers, but most sources put the total amount of deportees at between 400,000 and two million, with perhaps sixty percent of those being citizens of the country they were deported from. That’s between a quarter of a million and 1.2 million Americans exiled from the country based purely on their race.