Letter to Pierre Chouteau, reprinted in: Chittenden, Hiram Martin, The American Fur Trade of the Far West, 1902, appendix A.
Three Forks of the Missouri, April 21, 1810
Mr. Pierre Chouteau, Esq.,
DEAR SIR and BROTHER IN-LAW:
— I had hoped to be able to write you more favorably than I am now able
to do. The outlook before us was much more flattering ten days ago than
it is today. A party of our hunters was defeated by the Blackfeet on the
12th inst. There were two men killed, all their beaver stolen, many of
their traps lost, and the ammunition of several of them, and also seven
of our horses. We set out in pursuit of the Indians but unfortunately could
not overtake them. We have recovered forty-four traps and three horses,
which we brought back here, and we hope to find a few more traps. 
This unfortunate affair has quite discouraged our hunters, who are unwilling to hunt any more here. There will start out tomorrow, however, a party of thirty who are all gens a gage, fourteen loues and sixteen French. They go to the place where the others were defeated. I shall give them only three traps each, not deeming it prudent to risk more, especially since they are not to separate, and half are to remain in camp.
The party which was defeated consisted of eleven persons, and eight or nine of them were absent tending their traps when the savages pounced upon the camp. The two persons killed are James Cheeks, and one Ayres, an engage of Messrs. Crooks and McLellan whom Messrs. Silvester and Auguste (Chouteau) had equipped to hunt on shares. Besides these two, there are missing young Hull who was of the same camp, and Freehearty and his man who were camped about two miles farther up. We have found four traps belonging to these men and the place where they were pursued by the savages, but we have not yet found the place where they were killed.
In the camp where the first two men were killed we found a Blackfoot who had also been killed, and upon following their trail we saw that another had been dangerously wounded. Both of them, if the wounded man dies, came to their death at the hand of Cheeks, for he alone defended himself.
This unhappy miscarriage causes us a considerable loss, but I do not propose on that account to lose heart. The resources of this country in beaver fur are immense. It is true that we shall accomplish nothing this spring, but I trust that we shall next Autumn. I hope between now and then to see the Snake and Flathead Indians. My plan is to induce them to stay here, if possible, and make war upon the Blackfeet so that we may take some prisoners and send back one with propositions of peace—which I think can easily be secured by leaving traders among them below the Falls of the Missouri. Unless we can have peace with these (ma—?) or unless they can be destroyed, it is idle to think of maintaining an establishment at this point.
Assure Madame Chouteau of my most sincere esteem as well as your dear children, and believe me always your devoted
Pierre Menard.
We are daily expecting to see the Blackfeet here and are desirous of meeting them.