Answer: Petersburg
Richmond, Virginia served as the capital of the Confederate states for almost the whole Civil War. However, after a long siege from June 9, 1864, to March 25, 1865, Grant captured both Petersburg and Richmond.
The union forces first assaulted Petersburg, but as they were unsuccessful, they constructed trench lines from the eastern outskirts of Richmond to the eastern and southern outskirts of Petersburg. After the long campaign, on April 1865 , the Confederate forces abandoned both cities.