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.