Numbers 3. Report of Colonel William Crooks, Sixth Minnesota Infantry.

CAMP WILLISTON, DAK., August 5, 1863.

SIR: Pursuant to order of Brigadier General H. H. Sibley, this regiment reported at Camp Pope, Minn., for service in the expedition directed against the Sioux Indians. The march was taken up early on the morning of the 16th, and on the 26th day of June the forces encamped at the foot of Lake Traverse, a distance of 119 miles from Camp Pope. From this point a train was dispatched to Fort Abercrombie for supplies, the guard consisting of three companies of infantry, including Company H, of the Sixth Regiment, Captain [W. K.] Tattersall, one battalion of cavalry, Major [J. H.] Parker commanding, and one section of artillery, the whole under command of Lieutenant-Colonel [J. T.] Averill, of this regiment. The brigade left Lake Traverse on the 30th of June, and reached the first crossing of the Cheyenne River on the evening of the 4th of July, distant from the foot of Lake Traverse 74 miles. At this point, called Camp hayes, the command laid over six days, awaiting the arrival of the supply train from Fort Abercrombie. The train arrived on the 9th of July, and the expedition resumed the line of march on the morning of the 11th. From this point to the second crossing of the Cheyenne, where we arrived on the 17th, the distance was 83 miles.

On the morning of the 18th, we resumed the march, and made Camp Atchison, on Lake Emily, the day's march being 12 miles. At this point I was directed to lay out an intrenched camp, and a force was selected from the several regiments to hold the same, with a view to disembarrassing the active force of all men unable to march, and of all supplies not actually necessary in a more rapid pursuit of the enemy.

Companies G and C, of my regiment, were designated by me as part of the garrison, together with invalids from all other companies.

Having put the command in light marching order, on the morning of the 20th of July, with twenty-five days' rations, the command again commenced, with renewed energy, the pursuit of the Sioux; and at noon on the 24th, at a distance of 78 miles from Camp Atchison, a shout from the advance told that our pursuit had not been in vain. The savages lined the crests of the surrounding hills, covering their camp some 5 miles to the southwest. By direction of the general, the Sixth Regiment, together with Company M, of the Mounted Rangers, under command of Lieutenant [D. B.] Johnson, and a section of artillery, under command of Lieutenant [H. H.] Western, occupied, the east front, and threw up earthworks, supporting the guns. About this time Surgeon Weiser, of the Mounted Rangers, in company with others, rode up the heights and engaged in conversation with the Indians, who, true to their proverbial treachery, pierced his manly heart at the moment he offered them bread. Observing this act, I at once deployed Companies E, I, and K well to the front, and with Company E, under command of Captain [Rudolph] Schoeneman, together with Captain [Jonathan] Chase's company (A), of the Ninth Regiment, on Schoeneman's left, supported by Captains [T. S.] Slaughter and [W. W.] Braden, drove the savages for 3 miles, and prevented their turning our left.

Lieutenant-Colonel Averill was directed by me to advance three companies to support the extreme left, where a strong demonstration was being made, Major McLaren remaining in command of the reserve and camp.