The american civil war beacause you cant just search only that up. You will get lots of answers beacuse more than one thing happened then.
Delivery of war supplies and delegating certain space for commercial uses.
The answer for this question is: New England
The region of new England was the main target destination for the people who want to seek job opportunity during that time (mostly from Massachusetts)
Not only that, the economic growth in this region also give the people with enough resources to sustain their living so their mortality rate is really low.
