Jefferson is a city and the county seat of Jackson County, Georgia, United States. The population was 13,233 at the 2020 census, up from 9,43…Jefferson is a city and the county seat of Jackson County, Georgia, United States. The population was 13,233 at the 2020 census, up from 9,432 at the 2010 census. As of 2024 the estimated population was 17,215.