Called to the Bar of Upper Canada in 1840, John Sandfield Macdonald settled in Cornwall to practice law. He was elected to the Legislative Assembly of Upper Canada and remained there until 1867. From the outset of his political career, he associated with reformers and their program. From 1849 to 1851, he held the office of solicitor general in Robert Baldwin's cabinet and in 1852, was appointed Speaker of the Legislative Assembly.
Highly critical of Lord Elgin's politics, Sandfield Macdonald moved closer to George Brown as a spokesman for reformers in Upper Canada. But their co-operation was short-lived; George Brown advocated rep by pop and a highly centralized legislative union, while Sandfield Macdonald favoured a double majority, which would better safeguard the distinctive characteristics of United Canada's two regions. He envisioned a more flexible, less centralized federal authority.
Sandfield Macdonald was called on to form a government from 1862 to 1864. When his attempt to apply the principle of the double majority failed, he proposed a coalition of the various ideologies within a single government to counter Canada's political instability. This Great Coalition would be the work of George Brown, John A. Macdonald and George-Étienne Cartier, however. Sandfield Macdonald was excluded because he opposed a centralizing federalism and the inclusion of the Maritime provinces in the Union. Nevertheless, and despite his disagreement with the Québec Resolutions, Sandfield Macdonald accepted Confederation as an inevitability.
In recognition of Sandfield Macdonald's popularity, integrity and political know-how, John A. Macdonald named him premier of the new province of Ontario in 1867. He held this office until 1871, when poor electoral results and illness forced him to resign.
Hodgins, Bruce W. John Sandfield Macdonald, 1812-1872. Toronto : University of Toronto Press, 1971. 131 P.
Hodgins, Bruce W. "Macdonald, John Sandfield." The 1999 Canadian encyclopedia : world edition. Toronto : McClelland and Stewart, 1998.
Hodgins, Bruce W. "Macdonald, John Sandfield." Dictionnaire biographique du Canada. Québec : Presses de l'Université Laval, 1972. P. 506-516.