Answer:they were vital economic forces and transportation links, and the army could strengthen either side. Also, a border state on one side could help an support for the war Keeping control of the border states played an important role in the victory for the Union. These states gave the Union the advantage in troops, factories, and money.
The border states, which had not seceded, but separated the United States from the Confederate States, were of great importance to the Northern war strategy. In order to win the war, the Union Army would need to pass through the border states to invade the South. On the other hand, the border states, if they joined the Confederacy, would make it extremely easy for the Confederacy to attack and occupy Washington D.C.
