I will rely upon those that were there. A newspaper in March 1861:
It does not require extraordinary sagacity to perceive that trade is perhaps the controlling motive operating to prevent the return of the seceding States to the Union. Alleged grievances in regard to slavery were originally the causes for the separation of the cotton States; but it is apparent that the people of the principal seceding states are now for commercial independence. They dream that the centres of traffic can be changed from Northern to Southern ports. The merchants of New Orleans, Charleston, and Savannah are possessed with the idea that New York, Boston and Philadelphia may be shorn, in the future, of their mercantile greatness, by a revenue system verging upon free trade. If the Southern Confederation is allowed to carry out a policy by which only a nominal duty is laid upon imports, no doubt the business of the chief Northern cities will be seriously injured thereby.
The difference is so great between the tariff of the Union and that of the Confederated States, that the entire Northwest must find it to their advantage to purchase their imported goods at New Orleans rather than at New York. In addition to this, the manufacturing interest of the country will suffer from the increased importations resulting from low duties.
"That either revenue from duties must be collected in the ports of the rebel states, or the ports must be closed to importation from abroad... If neither of these things be done, our revenue laws are substantially repealed; the sources which supply our treasury will be dried up; we shall have no money to carry on the government; the nation will become bankrupt before the next crop of corn is ripe....Allow railroad iron to be entered at Savannah with the low duty of ten percent, which is all that the Southern Confederacy think of laying on imported goods, and not one ounce more would be imported at New York; the railways would be supplied from the southern ports."
I'm glad to see there is no longer any confusion on the cause of the war.
Walt