Final answer:
The Treaty of Oregon, signed in 1846, set the boundary between Canada and the United States at the 49th parallel from the Rocky Mountains to the Strait of Georgia, resolving the territorial dispute over the Oregon Country.
Step-by-step explanation:
The treaty that set a boundary between Canada and the United States in 1846 is the Treaty of Oregon. This agreement, also known as the Oregon Treaty, established the 49th parallel as the border between British North America (now Canada) and the United States from the Rocky Mountains to the Strait of Georgia. Prior agreements, such as the treaties signed in 1818 and 1827, had allowed for joint occupation of the Oregon Country by Great Britain and the United States. The Treaty of Ghent, signed in 1814, maintained the prior boundaries between British Canada and the United States. However, it was not until the Treaty of Oregon that a clear boundary was established, effectively resolving the territorial dispute over the Oregon Country.