 The brigade headquarters was organized on 19 June 1909 as Company M of the 1st Infantry, Colorado National Guard at Denver.The company was transferred to the 2nd Infantry on 19 November, retaining its letter, and on 15 August 1913 returned to the 1st Infantry as Company G. When the National Guard was called up for duty on the Mexican border in 1916, the company was mustered into Federal service on 19 June as Company B of the 1st Colorado Infantry Battalion.After the American entry into World War I, the unit was drafted into Federal service on 5 August 1917 and on 24 September became Company B of the 157th Infantry Regiment, part of the 40th Division.