The Treaty of Paris (1783), ending the American Revolutionary War, saw Britain cede significant territories south of the Great Lakes—lands then considered part of Quebec (British North America, later Canada)—to the newly independent United States. This included what’s now parts of Ohio, Michigan, and other Midwest states, roughly 10 million acres. While this was a British decision, it effectively transferred areas under Canadian colonial administration to the U.S., as Quebec’s boundaries stretched southwest before the treaty.
The Treaty of Ghent (1814), concluding the War of 1812, didn’t involve major new cessions but clarified and adjusted borders. Areas like parts of Upper Canada (now Ontario) that U.S. forces briefly held were returned to British control, but no significant Canadian land was permanently ceded here.
The Webster-Ashburton Treaty (1842) resolved disputes from the Aroostook War, adjusting the Maine-New Brunswick border. Canada (via Britain) ceded about 5,000 square miles (roughly 3.2 million acres) of disputed land to the U.S., while gaining 6,500 square miles elsewhere. This was a net loss for Canada in some areas but a mutual clarification, not a unilateral handover.
The Oregon Treaty (1846) set the 49th parallel as the boundary west to the Pacific, ceding the southern half of the Oregon Country (about 286,000 square miles) to the U.S. This land, jointly occupied by Britain and the U.S., included parts of what’s now Washington, Oregon, and Idaho. While not yet fully Canadian (it was British territory), it’s often framed as a loss for Canada’s future western expansion.
Smaller adjustments occurred later, like the Alaska Boundary Dispute (1903), where Canada lost a sliver of coastal access in the Yukon to the U.S. (about 1,000 square miles), settled by a tribunal favoring American claims.
Summary:
* Treaty of Paris (1783): 236,000 square miles.
* Webster-Ashburton (1842): 5,000 square miles.
* Oregon Treaty (1846): 286,000 square miles.
* Alaska Boundary (1903): 1,000 square miles.
* Total: 528,000 square miles.
A HALF MILLION square miles!
Treaty of Ghent took some time for word to reach America. In the meantime Andrew Jackson engaged the British in the Battle of New Orleans. It did not go well for the British.