Final answer:
Virginia, North Carolina, Arkansas, and Tennessee seceded from the Union after the bombardment of Fort Sumter.
Step-by-step explanation:
The four Southern states that seceded after the bombardment of Fort Sumter were Virginia, North Carolina, Arkansas, and Tennessee. These states decided to join the Confederacy and leave the Union in response to President Lincoln's call for troops to put down the rebellion. This decision ultimately led to the start of the Civil War.