In the past, a lot of (non-slave) people immigrated to the USA precisely because they were impoverished -- for example, Irish fleeing the Great Famine, among many others.
> "Give me your tired, your poor, / Your huddled masses yearning to breathe free, / The wretched refuse of your teeming shore."
Whether those words are as appropriate today may be another matter, of course.
I understand this example to be of historical note because it was exceptional. Many people came over for the promise of farmland or gold or something that they could capitalise on.
They came because they were poor. For a fictionalized account of Swedish immigrants, see Moberg's novel "The Emigrants". You might dismiss it as fiction, but the preface writes:
"To ensure the verisimilitude of his story, Moberg did extensive historical research in both Sweden and the United States. He studied county records in Smaland and read many collections of letters that immigrants in America had
sent to relatives in Sweden during the nineteenth Century. His studies also included trips to the Maritime Museum in Gothenburg. This research gave him a record of living conditions in nineteenth-century Sweden and a feel for life
aboard sailing vessels in the days when emigration had not yet become an industry backed by large steamship companies."
I'm curious if that's a figure for the number who enter and remain long-term, or does it include those who are quickly detained and expelled? I.e. does the Mexican border account for a million-plus annual increase in overall US population?
> "Give me your tired, your poor, / Your huddled masses yearning to breathe free, / The wretched refuse of your teeming shore."
Whether those words are as appropriate today may be another matter, of course.