Callaway County is a county located in the U.S. state of Missouri. As of the 2020 United States Census, the county's population was 44,283. Its county seat is Fulton. With a border formed by the Missouri River, the county was organized November 25, 1820, and named for Captain James Callaway, grandson of Daniel Boone. The county has been historically referred to as "The Kingdom of Callaway" after an incident in which some residents confronted Union troops during the U.S. Civil War.