The United States acquired the area of Oregon by a treaty with Great Britain in 1846. Oregon Territory was organized from the acquired area on August 14, 1848, and included all of present-day Oregon, Idaho, and Washington and part of western Montana and Wyoming. The territory was reduced in 1853 when Washington Territory was organized. In 1859, additional territory was transferred to Washington Territory, leaving Oregon with generally the same boundary as the present state. Oregon was admitted to the Union on February 14, 1859, as the 33rd state.