What are the 11 swing states?

In the Civil War, the Swing States were the slave-states of the Upper South that had not voted Confederate, but were in danger of doing so.

At the time of Lincoln's inauguration, there were eight of these. After the firing on Fort Sumter and Lincoln's appeal for volunteer troops, four of them declared for the Confederacy. The other four were Missouri, Kentucky, Maryland and Delaware. These were known as the Border States, and Lincoln's most urgent priority was to keep them loyal.

This left eleven states in the Confederacy. (There were never eleven Swing States).