Why was 'Union' valuable to the North, but not to the South?
Your're saying that the Union was not valuable to much of the South? That's pushing supposition a bit far, isn't it?
They did secede.
Let's look at some reasons:
* With secession the South controlled roughly 75% of the coastline.
And it was going to what with that coastline? There was no southern merchant fleet and,
There was a merchant fleet in Europe. You know, the ones that imported cotton.
with the exception of New Orleans, the ports were substandard.
A mattter that could change.
Along that majority of coastline, recount for me the yards capable of building a sea-going vessel.
New Orleans, Mobile, Savannah, Charleston, and a few places in Virginia.
* The South controlled the outlet of the Mississippi River.
And when the river was closed, the northwestern farmers switched to railroads. The closing was damaging, but not a coup de gras.
* The profits the North derived from trade with the South was cut off-
...several hundred millions per year to zero.
What the North got from the south was cotton, tobacco, rice, and a dab of sugar ... and the shipping and financing thereof. (See above; no southern merchant fleet.)
Yes, that is part of what they lose. The shipping will be replaced by England, France, and others.
An English or French ship brings in the imports, returns to Europe with cotton. No Yankee middleman. No shipping, no commissions. No imports to sell South.
I'd agree that Northern income might suffer a dip, which was why the industrialists pleaded with Buchanan and Lincoln to not start a war, (they figured the business would come back)
That was their stance for a while until they finally realized how much they were going to lose. They were the ones who paid for the war.