U.S. War Department, Map of the United States of America Showing Boundaries of the Union and Confederate Geographical Divisons and Departments, December 31, 1860 (1891)

The victory of Republican Abraham Lincoln, a known opponent of the expansion of slavery, in the 1860 presidential election, led many in the slaveholding South to believe it was no longer in their best interest to remain a part of the Union. On December 20, 1860, South Carolina's state legislature voted unanimously in favor of a declaration of secession, making it the first state to secede from the Union, with several more states to follow over the next six months. This map, part of the 1891 Atlas to Accompany the Offical Records of the Union and Confederate Armies, depicts South Carolina as the first Confederate state.