Historians offer various explanations about the causes of the American Civil War (1861-1865). I do not know much about the subject, and I just want to briefly present the explanation put forward by some Austrian Economists, because it sounds reasonable.
At the time of the American Civil War, the American North was industrialized and it was trying to compete with the European industries. For that reason the North was asking for high tariffs on imports, in order to protect its industries.
On the contrary, the economy of the American South was based on agriculture. Many states were cotton economies that were also using black slaves from Africa, while slavery had been forbidden at the American North and Europe.
The South did not want high tariffs, because they did not want to pay for more expensive manufactured goods from the American North. The American North was not happy with that, and it was demanding the South to abolish slavery, which would however increase the cost of production of cotton.
At the time the South had more influence over the Democrats, and the North had more influence over the Republicans, and therefore most democrats were asking for slavery to be legal and for tariffs to be kept low, while most republicans were asking the opposite.
At the end of 1860 the Republican Abraham Lincoln was elected as President of the United States, and he decided to go ahead with the abolition of slavery and the introduction of high tariffs on imports. Some Southern States decided to leave the United States and form a separate state. The crisis that followed led to the American Civil War of 1861-1865. The North won the war and slavery was abolished while high tariffs were implemented.
“Lincoln’s Tariff Wars”