The capital of the Union during the American Civil War was Washington, D.C. It served as the center of the Union war effort and was a strategic and vulnerable city, located between the Confederate state of Virginia and the border slave state of Maryland. Washington was used to mobilize and supply the Union Army, defend the eastern seaboard, and launch military operations toward Richmond, the Confederate capital. The Confederacy repeatedly targeted Washington throughout the war, believing that its loss would lead to immediate defeat