Guelph City Hall 1856
This fine example of classical architecture was begun in 1856 following the incorporation of Guelph as a town. It was designed by William Thomas, architect of St. Lawrence Hall, Toronto, and other important buildings throughout the province, and was completed in 1857. Constructed of Guelph stone, it contained a market house, offices and an assembly hall in which many notable persons were entertained, including the Hon. John A. Macdonald, later Canada's first Prime Minister. Alterations to the building were made in 1870 and a new hall was added in 1875. Except for the clock tower which was removed in 1961, the front portion of the structure retains its original appearance.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.