Jefferson is a historic city in Marion County in northeastern Texas, United States. The population was 2,024 at the 2000 census. It is the county seat of Marion County, Texas, and is situated in East Texas. The city is a tourism center, with popular attractions including: Jay Gould's Railroad car, the Sterne Fountain, Jefferson Carnegie Library, Excelsior House, the House of the Four Seasons, and the bayous formed by Big Cypress Bayou located in and around the city.