Map of the division of the states during the Civil War. Blue represents Union states, including those admitted during the war; light blue represents Union states which permitted slavery (border states). Red shows Confederate states. Unshaded areas were not states before or during the Civil War.
During the American Civil War, the Union meant the federal government of the United States, which was supported by the twenty free states and five border states. It was opposed by 11 Southern slave states. The Union states included the Western states of California, Oregon, and (after 1864) Nevada. They also included states then called the "Old Northwest" and now usually thought to be part of the Midwest. However, the Union has been also often called "the North", both then and now.
The Union states were: