Name the Territory Ceded in the Treaty of 1818 and involved the largest loss of land in US history?

The British ceded all of Rupert's Land south of the 49th parallel and east of the Continental Divide, including all of the Red River Colony south of that latitude, while the United States ceded the northernmost edge of the Missouri Territory north of the 49th parallel.

Explanation:

-The Convention of 1818 was a treaty between the United States and Britain that set the 49th parallel as the boundary between British North America and the US across the West.

-The British ceded all of Rupert's Land south of the 49th parallel and east of the Continental Divide, including all of the Red River Colony south of that latitude, while the United States ceded the northernmost edge of the Missouri Territory north of the 49th parallel.

-Known as the “Convention respecting fisheries, boundary and the restoration of slaves,” the Treaty secured fishing rights for U.S. fishermen along Newfoundland and Labrador, provided for joint control of Oregon territory, and marked the beginning of better relations between Britain and the U.S.

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d) a constitutional amendment

d. the right to establish a one-house legislature