The United States acquired the Oregon territory with the Oregon Treaty in 1846.
Explanation:
The area was jointly occupied after the treaty of 1818 in which the territory was given to both, British and Americans. The Americans knew that region as the Oregon County while the British known it as the Columbia District.
Between the years that both countries held the control jointly the coexistence within the same territory grew intolerable and finally by the year 1846 United State´s president Polk signed the treaty that sets boundaries to both countries in the 49° parallel. Polk did this because at that same time he was engaging in the Mexican- American War and he did not want to fight two wars, especially another one against the British forces.
The farmers often believed that if the process was made more difficult and drawn out it would be harder to violate the laws and citizens rights and liberties.
