[slibhb]

My sense is that most immigrants ended up in the north by far, which was richer, more densely populated and had better jobs. Slavery made it significantly harder for free laborers to find work in the south.

It is psychologically interesting that many people claim that slavery was the bedrock for the modern US economic. As if it's not enough to say "slavery was evil" but something more, like "slavery was evil AND without it the US would be a backwater". But I just don't see a lot of evidence for that theory being true.