Career
Born in Canandaigua, New York, Knowlton moved to Prairie du Chien, Wisconsin, where he practiced law. During the Mexican-American War, he raised a company of men, but they were stationed in Prairie du Chien during the war for frontier duty. In 1844-1846, Knowlton served, in the Wisconsin Territorial Council, of the Wisconsin Territorial Legislature.
In 1850, he was elected a Wisconsin Circuit Court judge and also served as a justice of the Wisconsin Supreme Court, until 1853, when a separate supreme court was formed.