The Border States is a term given to several states during the American Civil War. It usually refers to the states of Kentucky, Missouri, Maryland and Delaware. In 1863, some of the counties in the western part of Virginia left Virginia and became a new state called West Virginia. When West Virginia became a state, it was also called a Border State. These states stayed in the Union, but allowed slavery. Kentucky and Missouri had both Union and Confederate governments at one point. President Abraham Lincoln had to be very careful to keep these states in the Union. During the war, Maryland, West Virginia, and the Union government in Missouri ended slavery.