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.