Mason began his career as an engineer working with his father at the age of 17 on a canal construction project in
Albany, New York related to the
Erie Canal. He subsequently attended an engineering school in
Utica, New York. Mason was the first Chief Engineer of the
Illinois Central Railroad. Mason and his family moved in Chicago in 1865, when he was one of several engineers who worked to reverse the flow of the
Chicago River to improve health conditions and the cleanliness of
Lake Michigan.
Mayoralty Mason was elected Chicago mayor on a reform ticket
in 1869. During his administration, the 1871
Great Chicago Fire occurred. Mason responded by directing General
Philip Sheridan to place the city under
martial law. To date he is the last non Republican or Democratic Mayor of Chicago. Mason's tenure as mayor ended on December 4, 1871, when he was succeeded by
Joseph Medill. ==Later life and death==