Vincennes is a city in and the county seat of Knox County, Indiana, United States. It is located on the lower Wabash River in the southwestern part of the state, nearly halfway between Evansville and Terre Haute. Founded in 1732 by French fur traders, notably, Franois-Marie Bissot, Sieur de Vincennes for whom the Fort was named, Vincennes is the oldest continually inhabited European settlement in Indiana and one of the oldest settlements west of the Appalachians.According to the 2010 census, its population was 18,423, a decrease of 1.5% from 18,701 in 2000.