The Great Fire of 1849
On Saturday April 7, 1849, the citizens of Toronto awoke to a blaze that quickly consumed the centre of town. The fire started about one in the morning in a stable that once stood here. In the aftermath of the Great Fire with its flames seen as far away as St. Catharines, new fire codes were first adopted which are still in use today.
A new city was born atop the ashes of the old, spurred on by the construction of the present day St. James' Cathedral and St. Lawrence Hall.
Plaque via Alan L. Brown's site Toronto Plaques. Full page here.