In 1818, where did u. s. and british diplomats decide to place the u. s.-canadian border?
a. at the 15th parallel
b. at the 38th parallel
c. at the 49th parallel
d. at the 51st parallel

The answer is the 49th parallel. This was made possible with the Treaty of 1818 where this was the perimeter of lands belonging to the British that was located north west of the Great Lakes. The joint lands that was collectively owned by the British and Americans was Oregon County.

Fine until slavery ya ya haha