Which of the following wars was fought by the United States in the 1800s?

The Civil War was indeed fought by the United States in the 1800s, specifically from 1861 to 1865. This war was primarily a conflict between the Northern states, known as the Union, and the Southern states that seceded from the Union to form the Confederacy. The main issues at stake were the preservation of the Union and the contentious issue of slavery, which had deeply divided the nation. The Civil War had profound social, economic, and political implications for the United States and led to significant changes, including the eventual abolition of slavery with the 13th Amendment.

In contrast, the other wars listed occurred in different centuries: World War I took place from 1914 to 1918, the Korean War was fought from 1950 to 1953, and the Gulf War occurred in the early 1990s. Each of these conflicts is significant in its own right, but they do not fit within the timeframe of the 1800s.