Trenton is the county seat and fourth largest city of Gibson County, Tennessee, United States. As of the 2020 census, the population wa…Trenton is the county seat and fourth largest city of Gibson County, Tennessee, United States. As of the 2020 census, the population was 4,240. Trenton was established in 1824 as a county seat for the newly created Gibson County. The site was initially home to a trading post known as "Gibson-Port" that was operated by Thomas Gibson, a brother of the county's namesake, Colonel John Gibson. The city is named for Trenton, New Jersey.