Answer:
A Southern states believed that Abraham Lincoln intended to prohibit slavery and started to secede from the Union.
Step-by-step explanation:
The main cause of the Civil War (1861-1865) was the sharp contradiction between the different socio-economic systems that existed in one state - the bourgeois north and the slave-owning south.
In 1860, Republican Abraham Lincoln was elected President of the United States. His victory became a danger signal for the slave owners of the south and led to secession - the withdrawal of the southern states from the Union.