A major natural heritage feature now lost within infilling of the harbour and Ashbridge’s Bay, it was the primary connection between the mainland and the Toronto Islands.
Details of Site Location: The isthmus once formed the eastern boundary of Toronto harbour, and its southern end terminated at the sandbar which formed along the Lake Ontario side of the developing islands. Its eastern side merged with a host of marshlands, creeks, and ponds running into Ashbridge’s, Bay. Its northern end at the mainland, stretched between today’s Parliament Street and Cherry Street.
Current Use of Property: Former and current industries and roads cover the isthmus today.
Historical Description: The isthmus was formed over many centuries by sands eroded from Scarborough Bluffs and carried westward by lake currents to meet the silts deposited by the Don River. Together, these materials formed the isthmus and sandbar or sandy ridge at the outer edge of the islands. They enclosed Toronto harbour on the east and south sides. The Don River had as many as five mouths forming a delta, depending upon the period examined and the amount of human interference up to that time. In its most natural state, the isthmus was penetrated lazily by two outlets – sometimes more in high water periods. The Don outlet closest to the mainland was split, with one creek route meandering into Ashbridge’s Bay and the other entering the harbour close to the Gooderham & Worts site. This outlet appears not to have required any bridge in the early years. Farther south, at midpoint along the isthmus, another split in the creek route occurred, and from this point, the creek (or a Don route) turned east into Ashbridge’s Bay, and west through the isthmus into the harbour. In the early years of settlement, bridges crossed the outlet, although precisely how many were ever built is not known. Bridges would have been important in high water periods (every seven years), but the southerly outlet could be forded in low water periods as easily as its neighbour to the north. Elizabeth Simcoe, wife of the first Lieutenant Governor, frequently rode along the shoreline and across the isthmus to reach the island or sandbar. Her diary records many of these expeditions as her favourites. In later years, the young men of the Town of York held horse races along the isthmus, and the accounts make no mention of the need for bridges. Both sides of the isthmus were bordered by rushes and marshlands, and the actual edges of the isthmus were obscured by these, as was the shoreline itself.
Relative Importance: The primary importance of the isthmus lies in its connecting role between the mainland and the islands, and in the earliest uses made of it by residents of the Town of York and their various businesses located on the isthmus. The isthmus area was also the location of many later businesses, from foundries to boat-building companies, that played roles in the economic development of Toronto and in the necessary activities supporting Canada’s role in both World Wars.
Planning Implications: The isthmus must be regarded as a highly disturbed archaeological area, capable of revealing a great deal of Toronto’s historical and industrial development. Further disturbance of the infill and redevelopment of the area should follow extensive archaeological investigation, or the area should be left alone until archaeology is possible.
Reference Sources: R.H. Bonnycastle, Royal Engineers, No. 1 Plan of the Town and Harbour of York, Upper Canada, 1833; Elizabeth Simcoe’s Diary (any edition).
Acknowledgements: Toronto Field Naturalists; Ed Freeman, geologist; Maps Project collections.