The United States government (also known as the Union) did not agree that the states could leave and start a new government. Thus, the Union government refused to abandon all its forts in the states that wanted to secede. War began when the CSA attacked one of those forts, Fort Sumter in Charleston, South Carolina. This war is known as the American Civil War, and it lasted from 1861 to 1865. After some of the deadliest battles in U.S. history, Union forces gradually regained control of southern states. As Confederate forces surrendered, the Confederacy fell apart and the Civil War came to a close in 1865. Following the war, slavery was outlawed everywhere in the United States. The process of restoring the states of the CSA to the Union, called the Reconstruction of the United States, continued until 1877. 