Department of Oregon

The Department of Oregon was one of two Army Departments created September 13, 1858, replacing the original Department of the Pacific and was composed of the Territories of Washington and Oregon, except the Rogue River and Umpqua Districts, which were assigned to the Department of California. Its creation was authorized by General Orders, No. 10, of the United States Department of War, Adjutant-General's Office, September 13, 1858. Its Headquarters was at Fort Vancouver, in the Washington Territory.

Its first commander was Brevet Brigadier General William S. Harney, U.S. Army, from 1858 to June 1860. Shortly after he took command he sent troops under Captain George E. Pickett to San Juan Island precipitating the Pig War with Great Britain. Due to these altercations with the British he was recalled in June 1860 by the United States Secretary of War who reassigned Harney to the Department of the West, replacing him with the victor of the Oregon Indian Wars, Colonel George Wright, of the U.S. 9th Infantry Regiment, from June 8, 1860.

The Department of Oregon was merged into the restored Department of the Pacific on January 15, 1861, as the District of Oregon administering the same territories, under Col. Wright.

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