The American Civil War (1861-65) is a conflict between the northern states of the federal union of the States of America and the 11 separated southern states that formed the Confederacy of the United States. The outbreak of the conflict is the highlight of the decades of long disagreements over the doctrine of the rights of states, trade and slavery, but also of important socio-cultural values. The causes of war are many, of which the issue of slavery is certainly the most important.

By the end of the American Revolution (1783), the United States experienced rapid growth and development. New states are being created, and millions of immigrants are coming to the country. In the north of the country bloom trade and industry, capitalist society is developing. South of the country is oriented to agriculture, a plantation culture develops depending on the work of African-American slaves. It is exactly the institution of slavery that became the main stumbling block and conflict that, after decades of compromise, led to the secession of the southern states, the formation of the Confederation and the Civil War. The issue of slavery appears relatively early as one of the important issues of the future of the United States. In 1787, the Northwest Territory was abolished in the northwest. With this, the institution of slavery is reduced to the US South, and the Union is basically sharply geographically divided into the northern free and southern slave states. Import of slaves was finally banned in 1808. There were numerous discussions about this ban, and at the request of the politicians of the South, it was postponed. Trade in slaves was a very profitable practice on the plantations that depended exactly on slavery. With the enlargement of the Union, the issue of slavery is becoming more and more important, but also a growing stumbling block. The first political crisis erupted when Missouri entered the Union. Missouri wanted to enter the Union as a slave state. The free-trade countries of the Union wanted to enter as a free state. Only through the mediation of Senator Henry Clay the Missouri Compromise was concluded. For the political situation in the Union, the balance between free and slave states has become very important. South thought that if new states want, they should have the right to legalize slavery. The Northerners, however, believed that if his propagation was prevented, it would die out. By connecting the vast areas of the Midwest and California, this conflict became a hot issue. There were numerous and fierce debates on both sides. South needed the country and political equality. Losing the majority in the Congress, the South Africans did not want to lose the Senate; the desire was expressed to have a slave-girl for every free state in the Union. The extremists in the south have demanded that all new territories become open for slavery, extremists from the north to close, and moderate that the Missouri line was withdrawing to the Pacific, or that each country decide sovereignly on the issue.

By the compromise of 1850, California was declared a free state, New Mexico and Utah were constituted as countries where slavery was not mentioned, trade in slaves was banned in the District of Columbia, and an improved system for capturing and returning fugitive slaves was established. Still, the compromise opened up new issues, and in many cases the issue of slavery could only be resolved by war. During the constitution of Kansas and Nebraska, the issue of slavery caused major conflicts. According to the Missouri Agreement, Kansas and Nebraska were supposed to be free states, but the Compromise of 1850 opened the issue of introducing slavery (the preceding Utah and New Mexico). In the next couple of years, the situation worsened. In the South, the expansion of slavery is being sought, and the North is increasingly seeking complete restraint and abolition of slavery. This problem, together with the tense political situation after the presidential elections of 1860-1861 and the victory of Abraham Lincoln, led to a civil war.