States that did not side with either the North (Union) or the South (Confederacy) during the American Civil War were called border states.

These states were:

* Delaware

* Maryland

* Kentucky

* Missouri

* West Virginia (which separated from Virginia during the war)

These states were located geographically on the border between the North and South, and they were politically divided as well. Some of their citizens supported the Union, while others supported the Confederacy.

It's worth noting that these states were not truly "neutral" in the conflict. They were all involved in the war to some degree, and their decisions had a significant impact on the outcome of the war.