The US (where “open borders” are often characterized as national “suicide” by right-wing figures) had open borders well within living memory.

By ship? No. But you’re from Argentina and made it all the way up to the Rio and want to cross to work on US farms or whatever? Yeah whatever man, totally fine, just walk in. Anyone from the Americas was welcome, no waiting, no la migra hunting them, no nothin’

We didn’t change that until the ‘60s, and the only reason it didn’t cause a ton of problems immediately (farms at that time were already heavily dependent on migrant labor operating a bit under the table, and their lobbies were not quiet on the issue) was that enforcement was and has been, at times (and especially at first) mostly rather half-assed.