Stockton is a city and the county seat of Cedar County, Missouri, United States. The population was 1,683 at the 2020 census. Stockton was …Stockton is a city and the county seat of Cedar County, Missouri, United States. The population was 1,683 at the 2020 census. Stockton was platted in 1846. It was originally named Lancaster, but was renamed Fremont in 1847 in honor of John C. Frémont. In 1857 it was renamed again, in honor of Robert F. Stockton.