Answer:
Another cause often cited is the clear differentiation between the northern and southern economies (although many modern historians do not agree with the theory that economic differences were determinants in the outbreak of war). In the first, the great capitalist industry was growing, with a large concentration of salaried labor, in full swing and at the gates of the Second Industrial Revolution (to which the war contributed, with the new military technologies such as the battleships or the production of mass weaponry). These bourgeois groups from the north were represented by the new Republican Party, of a liberal nationalist type, which sought the implementation of protectionist policies.
On the other hand, the south remained anchored in an economic system that was unfavorable to capitalist development (mechanization and hiring of workers was cheaper than the maintenance of slaves). The Democratic Party would be the defender of slavery. This party had led the great expansion of the country to the south (activism in favor of the annexation of Mexican territory) and now stood as representative of the southern elites, which sought fundamentally the extension of the slave system and free trade for the export of materials premiums and the importation of manufactured goods without barriers.
The tension between the two economies only increased with the expansion of territories to the west, since both systems needed such expansion in the face of the international bullish situation.
