What were the opposing sides in the American Civil War referred to as?

The opposing sides in the American Civil War were referred to as the Union and the Confederate. The Union represented the northern states that remained loyal to the United States government, while the Confederacy comprised the southern states that seceded from the Union over issues primarily related to slavery and states' rights.

Referring to the Confederacy simply as "Confederate" is accurate because it encapsulates the identity of that side within the conflict. The term focuses on their belonging to the Confederate States of America, which was formed to assert their governmental authority separate from the Union.

Other choices, while they contain elements of the Civil War, are either incorrect or more generalized terms. The term "Union vs. Confederation" misrepresents the name of the Confederate side. "Federal vs. State" does not adequately capture the specific conflict of the Civil War as it oversimplifies the issues at stake. Lastly, "North vs. South" is an informal way to describe the conflict but lacks the political precision that "Union vs. Confederate" provides in a historical context.