Bluefield is a city in Mercer County, West Virginia, United States. The population was 9,658 at the 2020 census. It is the principal city of th…Bluefield is a city in Mercer County, West Virginia, United States. The population was 9,658 at the 2020 census. It is the principal city of the Bluefield micropolitan area extending into Virginia, which had a population of 106,363 in 2020.