Yes, I found it surprising when I first learned the fact (in the 1970s), because immigrants were pouring into all other parts of the United States in large numbers at the time. That includes places that were wholly undeveloped wilderness and also places that were battlegrounds outside the borders of the Confederacy.

It's even more surprising to me now, after years of reflection on my visits to Hong Kong in the 1980s, because the plain lesson of history is that welcoming immigrants is an excellent way to build up a destroyed economy and to provide more work both for the new arrivals and for the people who were already in the place that welcomes immigrants. There wasn't "work" (preexisting jobs) in the places where my ancestors or the majority of immigrants settled either, but there became work to do as the new settlers arrived.