[2] Simcoe County had been an electoral district in the Legislative Assembly of Upper Canada,[3] and its boundaries were not altered by the Union Act.

Those boundaries had originally been set by a statute of Upper Canada in 1798: That Matchedash, Gloucester, or Penetangueshine, together with Prince William Henry's Island, and all the land lying between the Midland District and a line produced due north from a certain fixed boundary (at the distance of about fifty miles north-west from the outlet of Burlington Bay) till it intersects the northern limits of the province, do constitute and form the County of Simcoe.

[4]In 1837, the Legislature further defined the boundaries of Simcoe County as follows: That the County of Simcoe, from and after the issuing of the said Proclamation, shall consist of the Townships of West Gwillimbury, Tecumseth, Adjala, Mono, Mulmer, Tosorontio, Essa, Innisfil, Nottawasaga, Sunnidale, Vespra, Oro, Orillia, (North and South division,) Medonte, Flos, Tiny, Tay and Matchedash, together with the Islands in Lakes Huron and Simcoe lying wholly or in greater part opposite thereto...[5] Since Simcoe was not changed by the Union Act, those boundaries continued to be used for the new electoral district.

[8] This article incorporates text from this source, which is in the public domain: An act for the better division of this province, SUC 1798, c. 5, s. 23.

This article incorporates text from this source, which is in the public domain: An Act to authorise the erection of the County of Simcoe into a separate District by the name of the District of Simcoe, SUC 1837, c. 32, s. 2.