How Much Did Oregon Cost? Nothing—It Was a Treaty, Not a Purchase

The United States did not purchase Oregon. The Oregon Country was jointly occupied by the U.S. and Britain until the Treaty of 1818 and later the Oregon Treaty of 1846, which set the 49th parallel as the border. The Adams–Onís Treaty (1819) with Spain ceded Spanish claims north of 42°, but no money changed hands for Oregon itself.