In all states except Louisiana, I believe.
How much was that in reality versus on paper?
I'm not so sure the U.S. would want any "Great Migration" to take place. Northern whites generally were opposed to slavery, but this did not - by any means - mean that they viewed black people as equals.
There were already plenty of barriers to the Slaves escaping, but not poor Whites. So too barring those leaving, or fleeing, the South
isn't going to work in an era (post-ACW to the 1910s) when you had open immigration from not only Europe but Asia!
The main problem for the North, perhaps might not be so much prejudice, TBH(though no doubt it'd play some role), as it would worries about the labor market having to deal with so many people coming at one time. To be truthful, I would suspect that many Northerners wouldn't be too happy about an extra 2 or 3 million Englishmen or Scots showing up all at once, either.
While I loved the rest of your post, I can't disagree more with the emboldened section, especially as immigrants coming down from Canada had a very much open door (no Ellis Island) on immigration. My ancestors came to the Northern USA both as refugees from a shattered South and to flee poverty from the Maritime Provinces and get jobs in the exploding industry to be found in mid-to-late 19th century South-Central Connecticut. Don't be fooled by the "Boom-and-bust" cycle for all things. Plenty of people did just fine even in bad times.
Racial prejudice was a huge factor. The North was a very racist place for most of its history. Opposition to slavery almost never had to do with a belief in egalitarianism for all races (John Brown was a rare exception, and he was shunned by "respectable" Northern society). Northerners might have sympathized with the plight of the slaves, but they didn't want to live among them. When African Americans did finally start moving in large numbers in OTL, at the end of World War I, there were massive race riots in Northern cities.
I disagree. There were many reasons for those race riots. Many were centered on areas of traditional Black settlement (Chicago frex), and the worst (Tulsa, Rosewood frex) were still in the South.
Northerners might not have been thrilled to have a ton of Englishmen move in either, but they'd have taken that any day of the week over an influx of African Americans. In OTL they could do little to stop it, but with an actual border to control, the U.S. almost certainly would have restricted immigration from the Confederacy.
Considering the prospective geographical nature of that non-OTL border and the wonderful success we've had
controlling a much more hostile one on the Mexican border (mountains, deserts) populated by Hispanics, lotsa luck trying to stop English-speaking American WASPs
Lotsa luck trying to get border guards to enforce said border laws. While hordes of Quebecois refugees might face problems due to language barriers, how are law enforcement personnel in the 19th century-early 20th century going to stop Anglo-Canadians? They can't.
Well, I doubt that immigration was ever going to be entirely unrestricted anyway, regardless of the era. The most likely scenario is that after a certain yearly quota is reached, they'd be directed to Canada or Liberia, or wherever.
Agreed. But then there is a cost factor. No $$$. Pre-ACW the runaways would go on their own to Canada to avoid recapture. NO ONE in a post-CSA Victorious TL in the USA would be favoring re-enslavement or return of runaways to the South, Turtledovian fantasies to the contrary (In Guns of the South he had the North converting
en masse to the Copperheads).
Hey, the Hillbilly Highway was real...
Lots of poor whites actually did "come north" during industrialization in the Nineteenth-Twentieth centuries, including big pulses in the teens and 1940s for the war mobilizations. Detroit (1) and Flint were know for it; the Appalachian whites were recruited because they were seen as "not" being likely to organize, at least early on...plus, they were Protestants (more or less...
)
Best,
1) Well, the Detroit Race Riots were a direct result of that. Not just refusing to hire unemployed Detroit Black residents, not just transporting in thousands of illiterate untrained Whites from hundreds of miles away to take those jobs, not only said Southern Whites taking their racist attitudes with them and fully expecting to be able to export them to one of the Blackest cities in America, but having the Detroit Blacks being evicted from their homes (renters, IDK about home owners) in the name of "wartime emergencies" to make room for said racist Whites. Small wonder that the rest was infamy.