Auburn is a city in south-central Maine, within the United States. The city serves as the county seat of Androscoggin County. The population w…Auburn is a city in south-central Maine, within the United States. The city serves as the county seat of Androscoggin County. The population was 24,061 at the 2020 census. Auburn and its sister city Lewiston are known locally as the Twin Cities or Lewiston–Auburn.