The official order is dated: 

[Special Order No. 114.]
HEADQUARTERS OF THE ARMY
Washington, August 24, 1881.

The following assignment is made of the general officers of the volunteer service, whose appointment was announced in General Orders No. 82, from the War Department

To the Department of the Cumberland, Brigadier-General Robert
Anderson commanding: 

Brigadier-General W. T. Sherman,
Brigadier-General George H. Thomas.

By command of Lieutenant-General Scott: 
E. D. TOWNSEND, Assistant adjutant-General.

After some days, I was relieved in command of my brigade and post by Brigadier General Fitz-John Porter, and at once took my departure for Cincinnati, Ohio, via Cresson, Pennsylvania, where General Anderson was with his family; and he, Thomas, and I, met by appointment at the house of his brother, Larz Anderson, Esq., in Cincinnati.  We were there on the 1st and 2d of September, when several prominent gentlemen of Kentucky met us, to discuss the situation, among whom were Jackson, Harlan, Speed, and others.  At that time, William Nelson, an officer of the navy, had been commissioned a brigadier-general of volunteers, and had his camp at Dick Robinson, a few miles beyond the Kentucky River, south of Nicholasville; and Brigadier-General L. H. Rousseau had another camp at Jeffersonville, opposite Louisville.  The State Legislature was in session at Frankfort, and was ready to take definite action as soon as General Anderson was prepared, for the State was threatened with invasion from Tennessee, by two forces:  one from the direction of Nashville, commanded by Generals Albert Sidney Johnston and Buckner; and the other from the direction of Cumberland Gap, commanded by Generals Crittenden and Zollicoffer.  General Anderson saw that he had not force enough to resist these two columns, and concluded to send me in person for help to Indianapolis and Springfield, to confer with the Governors of Indiana, and Illinois, and to General Fremont, who commanded in St. Louis.

McClellan and Fremont were the two men toward whom the country looked as the great Union leaders, and toward them were streaming the newly-raised regiments of infantry and cavalry, and batteries of artillery; nobody seeming to think of the intervening link covered by Kentucky.  While I was to make this tour, Generals Anderson and Thomas were to go to Louisville and initiate the department.  None of us had a staff, or any of the machinery for organizing an army, and, indeed, we had no army to organize.  Anderson was empowered to raise regiments in Kentucky, and to commission a few brigadier-generals.