August 14

1848 Oregon Territory was established by an act of Congress on August 14, 1848. As formed it included the present State of Oregon, the present Territories of Washington and Idaho, the part of the Territory of Montana west of the Rocky Mountains, and the part of the Territory of Wyoming west of the Rocky Mountains and north of the 42d parallel. When Oregon was admitted to the Union in February, 1859, the part of Wyoming that had been Oregon Territory became the eastern most edge of Washington Territory.