The major result of the American Civil War regarding state sovereignty was the affirmation of federal supremacy over states' rights. The conflict, fought from 1861 to 1865, stemmed largely from disputes over slavery and states' rights. Following the Union's victory, the notion that states could unilaterally secede was effectively dismantled, reinforcing the principle that the federal government held ultimate authority. This shift in power dynamics paved the way for significant changes in American society, including the passage of the Thirteenth, Fourteenth, and Fifteenth Amendments, aimed at ensuring civil rights for formerly enslaved people and reshaping the nation’s legal landscape.