Wich states were border states? why were these states conflicted on who to support in the

My mom told me this when we were there... Missouri?

In the context of the American Civil War (1861–65), the border states were slave states that did not declare a secession from the Union and did not join the Confederacy.
Four slave states never declared a secession which were, Delaware, Kentucky, Maryland, and Missouri. Four others did not declare secession until after the Battle of Fort Sumter and were briefly considered to be border states: Arkansas, North Carolina, Tennessee, and Virginia.