Name one war fought by the United States in the 1800s.

The Civil War is indeed one of the prominent conflicts fought by the United States in the 1800s. This war occurred between 1861 and 1865, primarily as a result of the longstanding controversy over the enslavement of Black people. The Civil War was a crucial turning point in American history, leading to the preservation of the Union and significant social and political changes, including the eventual abolition of slavery.

In contrast, the Revolutionary War took place in the 18th century, specifically from 1775 to 1783, as the thirteen American colonies fought for independence from British rule. The Vietnam War, fought in the 20th century from the late 1950s to 1975, involved the United States in a conflict aimed at preventing the spread of communism in Southeast Asia. World War I also occurred in the 20th century, primarily from 1914 to 1918, with U.S. involvement occurring later in the war, starting in 1917. Thus, these wars do not fit within the specified time frame of the 1800s.