<human>:  What is the history of the American Civil War?
<bot>: The American Civil War was a conflict that took place between 1861 and 1865 between the United States of America (the Union) and eleven Southern states that declared their secession and formed the Confederate States of America (the Confederacy). The primary cause of the war was the disagreement over the issue of slavery. Other factors in the conflict included a dispute over states’ rights and the southern states’ desire to preserve the institution of slavery. The Union ultimately prevailed and slavery was formally abolished. After the war ended in 1865, the nation began to rebuild as the period of Reconstruction began.