The U.S. Civil War was a conflict fought from 1861 to 1865 between the Northern states, known as the Union, and the Southern states, known as the Confederacy. The primary cause of the war was the disagreement over slavery and states' rights. The Union aimed to preserve the nation and abolish slavery, while the Confederacy sought to maintain their way of life, which included the institution of slavery. The war resulted in significant loss of life and widespread destruction. Key battles included Gettysburg and Antietam, and important figures included Abraham Lincoln, the President of the Union, and Robert E. Lee, the commander of the Confederate forces. The war ended with the surrender of the Confederacy in 1865, leading to the abolition of slavery and significant changes in American society.