Fond du Lac , city (1990 pop. 37,757), seat of Fond du Lac co., E central Wis., in a resort region at the south end of Lake Winnebago; inc. 1852. The city's economy is based on dairy farming and the manufacture of machine tools, leather goods, engines, and auto parts. A French fur-trading post in the late 18th cent., it later grew into a lumbering town. After the arrival of the railroad, it became an industrial city. Marian College of Fond du Lac and a branch of the Univ. of Wisconsin are there.