The Ingham County Courthouse is an historic government building located at 341 South Jefferson Street in Mason, Ingham County, Michigan. It occupies an entire city block bounded by South Jefferson, East Ash, South Barnes and East Maple Street. Constructed from 1902 to 1904, it is Ingham County's third courthouse and the second on this block, which is directly north of the site of the first courthouse. Designed by noted Lansing architect Edwyn A.