Ontario is a province located in the east-central part of Canada, the largest by population and second largest in total area.
Ontario is bordered by the Canadian provinces of Manitoba to the west and Quebec to the east, and five U.S. states (from west to east): Minnesota, Michigan, Ohio, Pennsylvania and New York to the south and east. It has coasts on Hudson Bay and the Great Lakes.
Ontario in Atlantis
The Dominion of Ontario was a semi-autonomous nation, affiliated with the British Empire, on the northeastern portion of the continent of Terranova. The United States of Atlantis sought Ontario as an ally when the former were fighting for independence from Britain, but Ontario refused.
Atlantis again supported rebellion in Ontario and elsewhere, leading to the War of 1809 with Britain. Atlantean buccaneers harassed Ontarian shipping, but the war ended with the status quo antebellum.
Britain continued to reign over Ontario in the latter part of the 19th century.
The borders of this Ontario remain unknown. It is included here for convenience. In "Audubon in Atlantis" it is revealed that there is a region called Canada; the political relation, if any, between Canada and Ontario is unexplored.
Ontario in The Disunited States of America
Ontario was an independent nation in North America.
Ontario in Southern Victory
Ontario was Canada's most populous province and the most important. Although not threatened directly during the Second Mexican War, the British had used the ports there as a launching pad for their attacks against US Great Lakes Cities. In the war's aftermath, the Canadians fortified the southwestern region more heavily than anywhere else along their border with the US.
During the Great War, the United States Army invaded across Niagara Falls and Windsor, beginning three years of bloody trench warfare in southern Ontario. Although the fortifications did slow the Americans down and cause great casualties, it didn't stop them. By 1917, much of the province was overrun by the time of the armistice and the rest was subsequently occupied.
In the ensuing peace, the citizens within the province rebelled in 1925, but were crushed.
Years later, when the Second Great War began in 1941, Canada's infrastructure became the USA's lifeline after the Confederates cut the country in two with Operation Blackbeard. In 1942, the people once more rebelled with the help of the British. Ontario saw the most action but eventually it too succumbed to the US Army.
Ontario in The Two Georges
In OTL, Canada was applied to both Ontario and Quebec by the British when the land passed to their control after the Seven Years' War. The former was also called Upper Canada and then Canada West. In the Georges' universe, "Canada" continued to be used for this province while the name "Ontario" was given to the province next westward of Canada, named Manitoba in OTL and most other timelines.
Ontario in Worldwar
In 1942, Southwestern Ontario was invaded by the Race when they landed, but stiff resistance from the Canadian Army prevented them from any further conquest. This conquest marked the furthermost north the Race ever got in their fighting on the North American continent.
Throughout the war, the Race maintained a tentative hold there, while the infrastructure became the Americans' lifeline, due to their own country being cut in two. When peace was declared in 1944, the Race withdrew from the region after recognizing Canada's independence.