It is a training component of the United States Army Reserve, and subordinate to the 104th Division based in Fort Lewis, Washington.

The 1st Brigade traces its lineage back to the old headquarters element of the division.

The 104th Infantry Division's original headquarters element was first constituted on 24 June 1921 as the 104th Division, before being organized and activated in October of that year in Salt Lake City, Utah.

[2] As a unit of the Organized Reserves, the division represented assets from the states of Washington and Montana, among other areas of the northwest United States.

[7] In 2005, the Base Realignment and Closure process included the closure of the Vancouver Barracks, and the 1st Brigade, 104th Division was subsequently relocated to Fort Lewis, Washington, though its duties remained the same.