And absolutely critical to the economy of New York and Washington D.C.
You keep leaving out that part because it doesn't fit your narrative.
In 1860, Slavery accounted for 3/4ths of all cargo carried by the New England New York shipping industry.
They fought that war to get that money back, not to abolish the source of that money.
In other words, they were more evil than the slave holders. Their god was Mammon.
Oh for God's sake, your claims are growing crazier by the hour.
Cotton was half, not 3/4, of US exports and more than half of that shipped from Gulf Coast ports directly to international customers, not through Northern ports.
So, if Northern ports accounted for less than half of cotton shipments, it means 3/4 of Northern shipments were of non-Southern origin.
FRiend, you whole hypothesis here has been falsified over and over again -- give it up!
DiogenesLamp: "They fought that war to get that money back, not to abolish the source of that money."
No, the United States went to war against the Confederacy because the Confederacy provoked, launched and formally declared war while supporting pro-Confederates in Union states.
That made the Confederacy an existential threat, far more so than ever Nazi Germany or Imperialist Japan 80 years later.