How did this map change following the Treaty of Washington in 1846? A: The Oregon Country who is divided between Britain and the United States at the 49th parallel
B: The Oregon Country was split into the Washington and Oregon territories using the 49th parallel
C: The boundary between the Oregon Country in Mexico shifted from the 42nd parallel to the Oregon trail route
D: the portion of the Oregon Country below the 49th parallel became part of Mexico, was the portion above the 49th parallel became part of Great Britain