William Mitchell was born near Mount Vernon in Knox County, Ohio.

He left the classroom and served as a captain in Company A of the 96th Ohio Infantry Regiment.

[4] On the evening of March 10, 1890, William Mitchell died suddenly of heart failure[3] at his residence on Second Street[3] in Bismarck, North Dakota.

[6] His deputy, Frederick W. Cathro, became interim superintendent until William J. Clapp was appointed to complete Mitchell's term in office.

William Mitchell is buried at Mound View Cemetery in Mount Vernon, Ohio.