Democratic dominance of the South originated in the struggle of white Southerners during and after Reconstruction (1865–1877) to reestablish white supremacy and disenfranchise blacks. The U.S. government under the Republican Party had defeated the Confederacy, abolished slavery, and enfranchised blacks.
Confederate troops fired on Fort Sumter in South Carolina's Charleston Harbor. Less than 34 hours later, Union forces surrendered. Traditionally, this event has been used to mark the beginning of the Civil War. So the second one.
