Jamestown is a city in and the county seat of Fentress County, Tennessee, United States. The population of the city was 1,959 at th…Jamestown is a city in and the county seat of Fentress County, Tennessee, United States. The population of the city was 1,959 at the 2010 census. Jamestown was established in 1823 as a county seat for Fentress County. It was incorporated as a city in 1837. Both Fentress County and Jamestown are named for prominent local politician James Fentress, who made the appeal for the new county to be carved out of Overton and Morgan counties.