The US government had imposed tariff policies that set a higher price on imported (foreign) manufactured goods. Because the South was an agricultural economy, it either had to ship down form the North or import from other countries most of the finished goods it consumed. Either option increased the cost of goods for Southerners over the prices paid by Northerners. Because the North was a largely industrial economy, and because raw materials imported for manufacturing were not subject to tariffs, the North faced no such burden. Additionally, because there was no income tax at this time, federal gov't revenue depended largely on tariff revenue -- which meant it was paid disproportionately by the South. This revenue was spent on railroads in the North and in other ways that unfairly benefitted the North while largely ignoring infrastructure and development in the South. South Carolina threatened secession as far back as 1828 over the unfair burden of the protective tariffs.
