Yesterday was flag day, so let's take a look at references to the American flag from the writings of the Western trappers.
The flag was typically a symbol of shelter, rest and peace. The flag was hoisted as a sign of greeting, and as a sign to trade.
Some Indians carried an American flag, indicating they were peaceful.

From Osborne Russell:
At sunrise an alarm of “Blackfeet!”
echoed thro. the Camp. In a moment all were under arms and enquiring “where are they” when
`twas replied “On the hills to the West”: I cast a glance along the high range of hills which projected
toward the river from the mountain and discovered them standing on a line on a line on a
ridge in their center stood a small pole and from it waved an American flag displaying a wish to
make peace about 30 of us walked up within about 300 yards of their line when they made a
signal for us to halt and send two men to meet the same number of theirs and treat for peace. Two
of the whites who could speak the Blackfoot language were appointed to negotiate while the
respective lines sat upon the ground to await the event. After talking and smoking for half an
hour the negotiators separated and returned to their respective parties Our reported them to be a
party of Pagans a small tribe of Blackfeet who desired to make peace with the whites and for that
purpose had procured the flag from an American trading post on the Missouri

From Larpenteur:
We landed safe and sound at Union on the last day of May, being the first boat up this season. We
arrived early in the morning and came in sight of the fort unobserved. The doors were all closed,
and not a living object was stirring except some buffalo, pasturing about 300 yards from the fort.
But the door was soon opened, the flag hoisted, and the artillery fired; to which salute the boat
responded. We were informed that the Sioux had been, and were still, so bad that the men dared
not keep the doors open. The Indians had at one time made a rush, and shot a squaw through the
thigh just as she was entering the fort. The Benton left about 3 p.m., having discharged 50 tons of
freight, which pleased the passengers very much.

Also from Larpenteur:
Our last camp was on the Big Muddy. Although we hoped that we had gotten rid of the horse
thieves, it was thought proper to keep up a strong guard, which consisted of one-half of the party
for each half of the night; but as it was very dark, the Assiniboines made out to take two of our
best horses, one of which was Mr. Mitchell’s. The chiefs said that they knew who had stolen the
horses, and told us not to be uneasy, for we should get the animals back again. They proved as
good as their word; our two horses were returned shortly afterward, though the interpreter’s was
never recovered. Thus, half consoled, we again got under way, and did not stop until we entered
Fort Union, which we did about 4 p. m., with a salute of many shots from the artillery, and the
large flag flying. This was on the 12th of October [1838]; and my reader can guess who felt good
after a six-weeks’ ride through the wild prairies.

From Dr. Thomas, a surgeon:
On the 21st we arrived at the first Mandan Village. This tribe had separated from the nation, and
had removed 30 miles down the river. Sheheken prevailed on them to return and become friends.
Here we discovered that he was the only chief of the one village, were we next day arrived. On our
approach a salute was fired from the barges, and answered by the village. On raising the American
flag, the barges was soon crowded with natives and mutual congratulations took place.

From John Work:
Saturday 17th Heavy rain in the night & the greater part of the day. The Flat Head Indians to the
number of 60 to 70 arrived headed by three chiefs, they were all on horseback and came singing
and firing guns with a flag flying. We answered their fire with a volley of Muskets.

Fort Laramie, by Alfred Jacob Miller, flying an American Flag

Always astonished at the wasting of powder and lead by firing salutes. Particularly by the Indians who never seem to have enough.

I think the word "pagan" as used by Russel, is a typo and should be "piegan" a sub tribe of blackfeet.

Spelling back then was more "creative" than it is today. Russell spelled it phonetically, but yes, the correct spelling now would be Piegan.
They were/are the largest of the Blackfeet bands.

You are so right. Some of the unedited journals are almost unreadable.