In the 1930s over a million people of Mexican origin left the US and headed south to Mexico in a little known episode that still haunts many of them.
It was called the Mexican Repatriation and the aim was to keep jobs for "real" Americans.
Linda Pressly visited the US amid fears that history might be about to repeat itself.
We asked for your comments following our programme and this is what you had to say.
As an American ex-pat residing in Australia I was shocked to hear this story. I lived in California for 14 years before coming here and I took my first degree in American History in the States. It always amazes me that we think that we have heard it all (I'm 63) and then along comes another revelation. Thank you for this extraordinary piece.
Chris Poulson, Tasmania
It is not just the workers that come to the US. It is also their families and the US has to take care of them. This costs California and federal government millions of dollars. Illegal immigrants don't pay taxes to help recover some of the costs. The incentives to come to the US are many and the issues of removing those incentives are complex. Stopping illegal immigration is the best place to start. As a side note, everyone coming to live in the US should have to learn to speak English. The government should not have to bear the burden of printing everything and providing translators in Spanish.
Pat L, California
This commemorates a regrettable past. Like so many regrettable past stories, those affected would like compensation. When shall those who seek financial compensation cease? There are talks of compensating descendents of slaves in the US. No doubt that those third, fourth, and fifth generation descendents would like that. But the victims were engaged in a legal institution. Likewise the deportees were removed as a result of enforcement of public policy. Perhaps we could next consider compensation for the descendents of former slaveholders who were deprived of a large amount of their wealth when slaves were emancipated.
John Bolt, Warthen, Georgia US
As a Mexican American, the last thing we need in California or any of the border states, is Mexico's problems imported here. Mexican citizens understandably want to the move to the US in order to have a better life. It's the only chance they have. But, the condemnation should not be placed on the US for demanding legal, orderly immigration but on the Mexican government for how poorly it has served and exploited its people. Otherwise, if the BBC in its usual anti-American zeal, is so interested in saving Mexican (illegal) immigrants, then I suggest the UK takes them in.
M Fernandez, California, US
Why shouldn't the authorities "sweep up", as you say, illegal immigrants whilst searching for criminals to be deported. Illegal means illegal. If you decide to live somewhere illegally, no matter who you are, then you must take the risks this involves. However, while developed countries are busy exploiting illegal workers when it suits them, it means the governments of the countries from which the illegal workers come, looking for a better life, never have to do anything to improve the lives of their citizens. At the root though is the developed world's desire for cheap food, cheap clothing, cheap labour - sort that out and you sort out the illegal worker problem.
The discussion is purely academic. Mexicans will move into the US if they have to. If their territories become uninhabitable, they will move. You can build walls and guard them with armed men and women but you won't keep them out. Walls have never kept out people who need to get past them.
Sarah Carless, Warwick
How horrifying to hear of the change of climate in LA. In 1974/5 I worked in a school in Wilmington (LA docklands) with a large proportion of Chicano students. The positive slant to education then to raise the profile of those with Mexican/central American backgrounds seems to have disappeared. Before California became part of the US it was Mexican and the population was Mexican. Hardly surprising that there are a lot of people who have Mexican origins, and hardly surprising that so many still want to go to the States to be employed in agriculture and the low paid jobs that only illegal immigrants would stomach.
Patricia Yorke, Barnet
Should the repatriation be part of the US curriculum? Yes, if the situation was true - then tell about it truthfully. Is a local council right to pass a law prohibiting renting to illegal immigrants? Yes, they are illegal. If the status of illegal immigrant is the same a legal immigrant - then why bother with legal immigration? Should the US give an amnesty for all illegal immigrants? No, because you only encourage more illegal immigration. Why would you want a situation where it is easier to ask for forgiveness than permission. By the way, I love Latinos and they are most welcome in the US. All that I ask is that they immigrate legally.
John T, Florida and London
The comments we publish are not necessarily the views of the BBC but will reflect the balance of views we have received. It is helpful if contributors state if they work for any organisation relevant to an issue discussed. Readers should form their own views on whether messages published represent undeclared interests, or views prompted by a common source.