The war fought between the northern and southern regions of the United States is known as the American Civil War. It lasted from 1861 to 1865 and primarily revolved around contentious issues like slavery and states' rights. The northern states, known as the Union, opposed the expansion of slavery, while the southern states, the Confederacy, sought to maintain and protect their slave-based economy. The war was marked by significant battles, societal upheaval, and profound consequences, leading to the eventual abolition of slavery. The Civil War profoundly transformed the nation, shaping its future and laying the groundwork for the civil rights movement.