Spartanburg is a city in and the seat of Spartanburg County, South Carolina, United States. The city had a population of 38,732 as of th…Spartanburg is a city in and the seat of Spartanburg County, South Carolina, United States. The city had a population of 38,732 as of the 2020 census, making it the 11th-most populous city in the state. The Office of Management and Budget groups Spartanburg and Union counties together as the Spartanburg, SC Metropolitan Statistical Area.