Caldwell County is a county located in Missouri, United States. As of the 2020 census, the county's population was 8,815. It is part of the Kansas City metropolitan area. Its county seat is Kingston. The county was organized December 29, 1836, and named by Alexander Doniphan to honor John Caldwell, who participated in George Rogers Clark's Native American Campaign of 1786 and was the second Lieutenant Governor of Kentucky.

Alexander William Doniphan was a 19th-century American attorney, soldier and politician from Missouri who is best known today as the man who prevented the summary execution of Joseph Smith, founder of the Church of Jesus Christ of Latter Day Saints, at the close of the 1838 Mormon War in that state. He also achieved renown as a leader of American troops during the Mexican–American War, as the author of a legal code that still forms the basis of New Mexico's Bill of Rights, and as a successful defense attorney in the Missouri towns of Liberty, Richmond and Independence.