Carl Junction is a city in Jasper County, Missouri, United States. The population was 8,143 at the 2020 census. Carl Junction was laid out …Carl Junction is a city in Jasper County, Missouri, United States. The population was 8,143 at the 2020 census. Carl Junction was laid out near a railroad junction by Charles Skinner, who gave the town his German first name of Carl. A post office called Carl Junction has been in operation since 1878.