History of North America

Four of the eight border states sided with North. Why was this important to Northern war effort?

Seven of the eight border states seceded from the Union, not four, and their support was crucial to the Union's success. The border states provided the North with vital resources such as food, horses, and manpower, and their location along the border with the Confederacy made them critical to the control of the Mississippi River, a major artery of commerce and warfare. Additionally, the loyalty of the border states helped to prevent the spread of secession to other states, and kept the Union from being completely surrounded by hostile territory.