The Department of the Columbia was a major command (Department) of the United States Army during the 19th century.
On July 27, 1865 the Military Division of the Pacific was created under Major General Henry W. Halleck, replacing the Department of the Pacific, consisting of the Department of the Columbia (replacing the District of Oregon) that now consisted of the State of Oregon and the Territories of Washington and Idaho and the expanded Department of California.
On March 18, 1868, the Army established the Department of Alaska under the Division of the Pacific. The Department of Alaska was discontinued on July 1, 1870, and Alaska was absorbed by the Department of the Columbia.
In June 1875, the part of the Territory of Idaho that lay east of the extension of the western boundary of Utah, and including Fort Hall, was detached from the Department of Columbia and added to the Department of the Platte.
When the Military Division of the Pacific was discontinued on July 3, 1891. Each of its three subordinate departments including the Department of the Columbia, then reported directly to the War Department.