What was one of the main causes of the Civil War?

SLAVERY was the central cause of the American Civil War (1861-1865). By 1860, deep divisions existed between Northern states (where slavery had been abolished) and Southern states (whose economy depended on enslaved labor). When Abraham Lincoln was elected president in November 1860 — running on a platform opposing the expansion of slavery — eleven Southern states seceded (withdrew) from the United States and formed the Confederate States of America. The Union (Northern states) refused to recognize the secession, and war began in April 1861 when Confederate forces attacked Fort Sumter in South Carolina. Other acceptable USCIS answers include: states' rights; economic reasons (related to slavery). The war lasted four years and resulted in approximately 620,000 military deaths — more American deaths than any other war. President Lincoln issued the Emancipation Proclamation on January 1, 1863, declaring enslaved people in Confederate states to be free. The Union's victory in 1865 was followed by the 13th Amendment (1865) abolishing slavery throughout the United States. The Reconstruction era (1865-1877) attempted to rebuild the South and integrate formerly enslaved people as full citizens, with mixed and ultimately limited success due to the rise of Jim Crow laws.