1791–1867 Upper Canada The Constitutional Act of 1791 recognized this development, as it split the Province of Quebec into the Canadas, Lower Canada east of the St. Lawrence-Ottawa River confluence, the area of earliest settlement; and Upper Canada southwest of the confluence. John Graves Simcoe was appointed Upper Canada's first Lieutenant-Governor in 1793. War of 1812 Owing to grievances from the impressment of American sailors by the British, and suspected British support of Native Americans in the American Northwest Territory, the United States declared war on the United Kingdom on July 1, 1812. Given its proximity to the United States, colonies in British North America, including Upper Canada found itself an active theatre of war throughout most of the conflict. The earliest offensives of the war took place near southwestern Ontario and the upper Great Lakes region, with American forces briefly crossing into present day southwestern Ontario, before a British-First Nations force launched an offensive into the Michigan Territory. However, on September 10, 1813, after the Americans gained control of Lake Erie, British forces evacuated Detroit, and eventually decided to withdraw from the entire area. American forces under William Henry Harrison caught up to the retreating British-First Nations force, decisively defeating them at the Battle of the Thames. Tecumseh, leader of a First Nations confederation, was killed shortly after the remaining British forces decided to fall back to Burlington; disrupting the military alliance between British and First Nations. Several invasion attempts by American forces were also attempted at the Niagara Peninsula. On October 13, 1812, an American invasion attempt was prevented at the Battle of Queenston Heights; although the commander of British forces in Upper Canada, Major-General Isaac Brock, was killed during the battle. On April 27, 1813, American forces raided and briefly occupied York, the capital of Upper Canada. A month later, American forces captured Fort George prompting the British to retreat to the Burlington Heights. However, further advances into the peninsula by American forces were halted at the battles of Stoney Creek and Beaver Dams; prompting the Americans to eventual withdraw from the peninsula on December 10, 1813. An American invasion force advancing towards Montreal was also repulsed at the Battle of Chrysler's Farm on November 13, 1813. In the summer of 1814, the Americans conducted another invasion of the Niagara Peninsula, successfully defeating the British at the Battle of Chippewa. However, American forces were prompted to withdraw