Which of the following was not a cause of the Civil War? * Sectionalism
Slavery
State's Rights
Nativism

Nativism

Explanation:

Civil war was one of the historic event in American history that happened from 1861 to 1865. It was fought between northern and southern states of America.

Sectionalism , slavery  and state's rights were three main or major reasons of civil war but nativism was not.

Nativism is defined as the policy that favors native people but in Civil War nativism was not the reason as people were not fighting for nativism but from other reasons such as sectionalism , slavery  and state's rights.

Civil war is defined as the war between intrastate so it can not be caused by nativism.

Hence, the correct answer is "Nativism".