The borders of Ontario were provisionally expanded north and west. When the Province of Canada was formed, its borders were not entirely clear, and Ontario claimed to eventually reach all the way to the Rocky Mountains and Arctic Ocean. With Canada's acquisition of Rupert's Land, Ontario was interested in clearly defining its borders, especially since some of the new areas it was interested in were rapidly growing. After the federal government asked Ontario to pay for construction in the new disputed area, the province asked for an elaboration on its limits, and its boundary was moved north to 51° north, and west to a line running north from Hunter's Island.

This was built with the shapefiles:

• Territorial Evolution, from the University of Toronto: https://doi.org/10.5683/SP2/IQ7E0X
• Global Islands: https://doi.org/10.5066/P91ZCSGM
• United States maritime borders: https://nauticalcharts.noaa.gov/data/us-maritime-limits-and-boundaries.html
• United States details from the Newberry Library: https://digital.newberry.org/ahcb/
• Canada detailed administrative divisions: https://www12.statcan.gc.ca/census-recensement/2021/geo/sip-pis/boundary-limites/index2021-eng.cfm?year=21