Americus is the county seat of Sumter County, Georgia, United States. As of the 2020 census, the city had a population of 16,230. It is the princ…Americus is the county seat of Sumter County, Georgia, United States. As of the 2020 census, the city had a population of 16,230. It is the principal city of the Americus Micropolitan Statistical Area, a micropolitan area that covers Schley and Sumter counties and had a combined population of 36,966 at the 2000 census.