William was elected to Toronto City Council as the Alderman for St. Lawrence Ward in 1836, a position his father held for one year until he was unseated in 1835 by conservative opposition.
His brothers John and Jonathan Cawthra served in the War of 1812 at Detroit and Queenston under Sir Isaac Brock.
He and his wife lived in a townhouse at the corner of King and Bay Streets (the current site of the Bank of Nova Scotia's main headquarters).
William was a founding and active member of the Toronto House of Industry, established in 1837 with a similar model to Dickensian workhouses, helping those in the city who were desperate for food, distributing coal to assist the needy to survive the harsh Toronto winters, providing temporary and permanent accommodations and assisting abandoned children or those who were orphans.
[3] William Cawthra died without heirs, leaving an estate estimated between $2,000,000 and $3,000,000 which was divided between his wife and his nieces and nephews.
His beautiful house at King and Bay long remained as his monument, but he is a political and business figure of whom there is little record or history with the exception of a small square and a city park.