Sioux south of the Missouri River, and will, in all likelihood, concentrate on the Upper Missouri, somewhere above the mouth of Grand River, to obstruct navigation and prevent the passage of emigrants up the river or across the plains. This information reaches me from several directions, and is as reliable as information concerning Indians can possibly be. There is little doubt that such is now the intention of these bands. Sully, re-enforced with all the available cavalry from Minnesota, which will join him at Bordache Creek, on the Missouri, as early as possible in the spring, will move up the Missouri with about 2,600 men to attack these bands.
If they carry out their purpose, to unite on the river and give battle, his campaign will soon be brought to a successful termination, and he can then make all desirable arrangements to assure the safety of travel. If, however, the Indians fail to unite, General Sully will divide his command and pursue the detached bands to the interior and endeavor either to force a battle or make a satisfactory peace. In any event a portion of his command will traverse nearly the region you suggest in the course of the summer, i. e., from Fort Pierre, by way of the Black Hills and the Yellowstone, to the upper Missouri. The number of warriors which the bands I have enumerated can readily assemble on the upper Missouri does not fall short of 5,000, so that until it is ascertained whether this concentration is made I cannot divide Sully's force, nor can any portion of that force escort emigrant trains without being entirely withdrawn from Indian operations.
As regards the emigration by way of Laramie, I would suggest that it is far more convenient to send an escort with them from that post than from any available force in this department.
I send you inclosed, also, a printed notice which I have published to emigrants.* It points out to them all that is necessary to assure a safe journey. If they neglect the advice given, and which every man familiar with Indians and prairie travel will repeat to them, they surely cannot complain. I need not say that I shall do all I possibly can with the means at my command to assure safety of travel over the plains; but in order to effect this the power of the hostile Indians must first be broken. A reference to my instructions to Generals Sully and Sibley will acquaint you with all the details of proposed operations.
I am, general, respectfully, your obedient servant,
MISSISSIPPI SQUADRON FLAG-SHIP BLACK HAWK,
Off Alexandria, La., March 21, 1864.
Brigadier General CHARLES P. STONE,
Chief of Staff, &c., Alexandria:
GENERAL: In the midchannel there is exactly 6 feet and 1 inch, while over the rocks there is only 3 feet. A powerful light-draught steamer will be required to pass over, as in case she was swung round by the current (6 miles per hour) against the rocks she would be lost.
Very respectfully, your obedient servant,
DAVID D. PORTER,
*Of March 14; see p. 608.