A couple of problems with your scenario. If imported goods were paid almost exclusively with exports then by rights imports should have dried up to almost nothing during the rebellion. After all, Southern agricultural goods did make up the overwhelming majority of exports, the rebellion certainly cut off that trade, and if precious metals were the only alternative, as you claim, then the North should have run out of that in fairly short order. But instead of trade drying up the opposite happened. Tariff income in the year prior to the rebellion was in the neighborhood of $60 million. Tariff revenue for FY1864 was well over $110 million. Factor in inflation and tariff increases and you still result in considerable increase in imports. And then when the rebellion ended and the Southern agricultural industry was devestated imports continued to increase. So either imports were not as closely tied to exports as you claim, or imports were paid for with cash on both sides of the ocean before, during , and after the rebellion.