Oregon Territory, as originally organized, in 1848
Oregon Territory (blue) with Washington Territory (green) in 1853
Oregon Territory's At-large congressional district is an obsolete congressional district that encompassed the area of the Oregon Territory. In 1853, the northern half of the territory was reorganized into the Washington Territory.
After Oregon's admission to the Union as the 33rd state by act of Congress on February 14, 1859, this district was dissolved and replaced by Oregon's At-large congressional district. At the same time, the eastern portion of the territory was annexed to the Washington Territory.