Legislature of the Province of Canada
After rioters burned the legislative building at Montreal in 1849 during the Tory protest over the Rebellion Losses Bill, the seat of the provincial government alternated between Toronto and Quebec. The sessions of 1850, 1851 and 1856 to 1859 were held in buildings originally erected (1829-1832) for the Legislature of Upper Canada in York, later Toronto. These buildings, which occupied the block bounded by Wellington, Simcoe, Front and John Streets, were demolished in 1904.
Plaque via Alan L. Brown's site Toronto Plaques. Full page here.