He served on in Montreal's city council as councillor (1850–51) and later as alderman (1852–57) for the district of Saint-Antoine. As a municipal politician, he promoted the construction of Canal de l'Aqueduc, an aqueduct in Montreal. He also served as president of the Montreal Board of Trade in 1861.
He served on the board of directors of the Montreal City and District Savings Bank (later known as Laurentian Bank of Canada), Montreal Telegraph Company, Merchants’ Bank and Citizens’ Insurance Company of Canada.
He married Lucy Huntington Greene (April 15, 1814 – May 29, 1890). They had four sons and four daughters.
The City of Montreal named Atwater Street after him in 1871, and the following Montreal landmarks are named after the avenue:
- Atwater Metro Station
- Atwater Library and Computer Centre, operated by the Mechanics' Institute of Montreal.
- Atwater Market
- "Edwin Atwater". Dictionary of Canadian Biography (online ed.). University of Toronto Press. 1979–2005.