[3] Northumberland County had originally been bounded by on the south by Lake Ontario and extended north, as described by a proclamation of the first Lieutenant Governor of Upper Canada, John Graves Simcoe, in 1792, and as further defined by a statute of Upper Canada in 1798.

[4][5] Prior to the Act of Union, Northumberland County had been represented by two members in the Legislative Assembly of Upper Canada.

[9] It was succeeded by two electoral districts in the House of Commons of Canada, Peterborough East and Peterborourgh West,[10] and two ridings of the same names in the Legislative Assembly of Ontario.

[11] This article incorporates text from this source, which is in the public domain: Proclamation, Lieutenant Governor John Graves Simcoe, July 16, 1792.

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, ss.