Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Sullivan County is a county located in the U.S. state of Tennessee. As of 2000, the population was 153,048. Its county seat is Blountville. Sullivan County is part of the Kingsport Bristol (TN) Bristol (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. According to the U.S. Census Bureau, the county has a total area of 430 square miles (1,113 km²), of which, 413 square miles (1,070 km²) of it is land and 17 square miles (43 km²) of it (3.88%) is water. Sullivan County''s boundary with Carter County and Johnson County is defined as the ridgeline of Holston Mountain.