John C. Calhoun (1782 - 1850) was an American statesman, political theorist, and a key figure in the early 19th-century U.S. government. Born in South Carolina, Calhoun served as a congressman, senator, vice president (under John Quincy Adams and Andrew Jackson), and secretary of war. He was a staunch defender of states' rights and slavery, becoming one of the most prominent advocates for Southern interests in the years leading up to the Civil War.

Calhoun is best known for his theory of "nullification," which argued that states could nullify federal laws they deemed unconstitutional. He believed in a strict interpretation of the U.S. Constitution, and his views on slavery and states' rights deeply influenced Southern politics.

Though initially a nationalist, Calhoun's political ideology evolved to focus on defending slavery and states' rights, making him a central figure in the debate over the expansion of slavery in the United States. He passed away in 1850, shortly before the nation would face the secession crisis and Civil War.