The Neils and Mackenzie settled in Kingston, Ontario. The limestone in the area proved too hard for his stonemason tools, and not having money to buy new tools, Mackenzie took a job as a labourer constructing a building on Princess Street. The contractor on the job claimed financial difficulty, so Mackenzie accepted a promissory note for summer wages. The note later proved to be worthless. Subsequently, Mackenzie won a contract building a bomb-proof arch at Fort Henry. He later became a foreman on the construction of Kingston's four Martello Towers - Murney Tower, Fort Frederick, Cathcart Tower, and Shoal Tower. He was also a foreman on the construction of the Welland Canal and the Lachine Canal. While working on the Beauharnois Canal, a one-ton stone fell and crushed one of his legs. He recovered, but never regained the strength in that leg. While in Kingston, Mackenzie became a vocal opponent of religious and political entitlement and corruption in government.