… is from pages 246-247 of Stanley Lebergott’s great 1984 book, The Americans: An Economic Record (footnote deleted):
Historians with a taste for paradox (or dubious economics) have discovered that the Civil War brought unprecedented economic growth to the United States. No longer hampered by the South’s agrarians, Northern industrialism took over the nation after the war. Northern production surged forward.
This belief that the war did stimulate production rests on one observation: Northern production rose after the war. But output had been increasing for decades before the war….
We can, however, infer that the war probably slowed American industrialization, had the alternative to war been yet another “peaceful” secession crisis. For death and suffering would not then have afflicted hundreds of thousands, North and South. Living on, and working, these workers would have lived to teach their skills to the next generation. And those who became entrepreneurs would have provided new productive ideas, otherwise lacking.