Osgoode Hall
Named after the province's first chief justice, Osgoode Hall was begun as the headquarters of the Law Society of Upper Canada in 1829. The east wing was built by 1832, with the centre and west wing being added between 1844 and 1846. The centre section was reconstructed in grand style from designs by the prominent Toronto architectural firm of Cumberland and Storm between 1856 and 1859. This edifice ranks among Canada's architectural and historical treasures. Osgoode Hall continues to house the Law Society, and has since 1846 been the seat of provincial superior courts.
Plaque via Alan L. Brown's site Toronto Plaques. Full page here.