The significance of the states is They were slaveholding states that remained with the Union.
Why did the states remain with the union
During the American Civil War, certain states allowed slavery but chose to stay in the Union rather than join the Confederacy. Known as "border states," including Delaware, Maryland, Kentucky, and Missouri, they had various reasons for this decision.
Their economies, while reliant on agriculture, were not as dependent on slavery as the Deep South. Geographically situated between the North and South, they held strategic importance for transportation and communication.