On July 12, 1831, 19-year-old Stevens T. Mason is named secretary of the territory of Michigan when the former secretary, his father John Mason, is sent on a mission to Mexico by President Andrew Jackson. At about the same time, Territorial Governor Lewis Cass became Jackson’s Secretary of War. George Bryan Porter was appointed by Jackson to replace Cass, but he was frequently absent and Mason was, for all practical purposes, the acting governor during this time, leading to his nickname of the “Boy Governor.”
Source : Detroit Historical Society Facebook page