Final answer:
The American Civil War was primarily caused by the issue of slavery and disagreements over states' rights versus federal power, with the election of Abraham Lincoln as a trigger for secession.
Step-by-step explanation:
The American Civil War, which took place from 1861 to 1865, was primarily caused by the issue of slavery. The conflict arose due to disagreements between the Northern states, which opposed slavery, and the Southern states, which relied heavily on slave labor in their agricultural economy.
Another contributing factor was the debate over states' rights versus the power of the federal government. The Southern states believed in the concept of state sovereignty and felt that the federal government was encroaching on their rights.
Finally, the election of Abraham Lincoln as President in 1860 acted as a trigger for secession, as many Southern states feared that his anti-slavery stance would threaten their way of life.
Learn more about causes of the American Civil War