Bluff City is a city in Sullivan County, Tennessee. The population was 1,733 at the 2010 census. It is part of the Kingsport-Bristol-Bristol, T…Bluff City is a city in Sullivan County, Tennessee. The population was 1,733 at the 2010 census. It is part of the Kingsport-Bristol-Bristol, TN-VA Metropolitan Statistical Area, which is a component of the Johnson City-Kingsport-Bristol, TN-VA Combined Statistical Area, commonly known as the "Tri-Cities" region.