What was a significant outcome of the American Civil War?

The abolition of slavery was a significant outcome of the American Civil War, as it fundamentally transformed the social and economic landscape of the United States. The war was primarily fought over the contentious issue of slavery, particularly in the Southern states where the economy heavily relied on slave labor. The conflict ultimately led to the passage of the Thirteenth Amendment to the Constitution in 1865, which formally abolished slavery in the United States.

This outcome had profound implications for millions of African Americans who were liberated from bondage and gained a renewed status as citizens, though the struggle for civil rights and equality would continue long after the war ended. The abolition of slavery is considered a milestone in American history, setting the stage for further social justice movements and reshaping the nation's values and legal structures concerning human rights.

The other choices, while related to historical topics, do not pertain directly to the most impactful and lasting consequence of the American Civil War. Establishing U.S. independence occurred in the 18th century, trench warfare is primarily associated with World War I, and the defeat of British forces pertains to the American Revolution rather than the Civil War. Thus, the abolition of slavery stands out as a central achievement of the Civil War era.