March 11, 1862
Issued by President Abraham Lincoln on March 11, 1862, War Order Number 3, consolidated three western departments, including the Department of the Ohio, into the Department of the Mississippi, commanded by Major-General Henry Halleck.
PRESIDENT'S WAR ORDER, NO. 3.
Washington, March 11, 1862.
Major-General McClellan, having personally taken the field, at the head of the Army of the Potomac, until otherwise ordered, he is relieved from the command of the other military departments, he retaining command of the Department of the Potomac.
Ordered further: That the two departments now under the respective commands of Generals Halleck and Hunter, together with so much of that under General Buell as lies west of a north and south line indefinitely drawn through Knoxville, Tennessee, be consolidated and designated the Department of the Mississippi; and that, until otherwise ordered, Major-General Halleck have command of said department.
By Order of the Secretary of War
L. Thomas, Adjutant-General
Wm D. Whipple, Assistant Adjutant-General