Sullivan County was created in 1779 from a portion of Washington County, and named for John Sullivan who was a general in the Revolutionary War. Long Island of the Holston located in Kingsport was the site of Fort Robinson, constructed in 1761 following the fall of Fort Loudoun further to the south, making the Sullivan area one of the earliest settled areas of Tennessee. The county has a total area of 430 square miles and a population count of 158,348 residents.