Border states

The border states are a handful of states in the U.S that were torn between the Union and the Confederacy during the American Civil War. With geographic, social, political and economic connections to both the North and South, the border states were critical to the outcome of the war.

The border states are usually described as: Maryland, Delaware, Kentucky and Missouri. The border states were defined, in part, by permitting slavery but not seceding from the Union to join the Confederacy.

(Non-state border regions that were also critical to the war's outcome included the areas that later became Oklahoma and West Virginia.)