Name one war fought by the U.S. in the 1800s.

The Civil War is a significant conflict in U.S. history that took place from 1861 to 1865, and it was fought between the Northern states (the Union) and the Southern states (the Confederacy). This war arose primarily over issues such as states' rights, slavery, and the economic differences between the regions. The outcome of the Civil War had profound implications for the United States, including the preservation of the Union, the abolition of slavery, and significant social and political changes in the aftermath.

In contrast, the other wars listed took place in different periods. World War I occurred from 1914 to 1918, the Korean War was fought between 1950 and 1953, and the Cold War, while it had military engagements, was a prolonged period of geopolitical tension between the Soviet Union and the United States that lasted roughly from the end of World War II until the early 1990s. Therefore, the choice of the Civil War as a war fought by the U.S. in the 1800s is historically accurate and relevant.