On July 26, 1806, the weather was unusually cold and rainy along the Marias River, and Meriwether Lewis was in a gloomy mood. His men broke camp at a place he had dubbed “Camp Disappointment.” Split off from William Clark and the rest of the expedition, Lewis had taken three men— George Droulliard and brothers Joseph and Reuben Field—on a detour to explore the northern reaches of the Marias in the hopes of finding a tributary that extended to 50° north latitude, which would have given the United States a claim to a more northern natural boundary of the Louisiana Purchase. Unfortunately, Lewis had found no such tributary, and his hope of finding an easy portage route between the Marias and Saskatchewan rivers hadn’t panned out either. Such a route would have opened the possibility of diverting some of the lucrative Canadian fur trade into American territory.
As Lewis, Drouillard, and the Fields brothers continued down river, Lewis suddenly realized they were not alone. He recorded in his journal:
the country through which this portion of Maria’s river passes to the fork which I ascended appears much more broken than that above and between this and the mountains. I had scarcely ascended the hills before I discovered to my left at the distance of a mile an assembleage of about 30 horses, I halted and used my spye glass by the help of which I discovered several indians on the top of an eminence just above them who appeared to be looking down towards the river I presumed at Drewyer. about half the horses were saddled. this was a very unpleasant sight, however I resolved to make the best of our situation and to approach them in a friendly manner.
Lewis believed the men to be Minnetare (or Atsina) Indians, but in fact they were Piegan Blackfeet, and they were equally surprised to find the Americans in their hunting grounds. The Blackfeet controlled most of the vast territory stretching almost from North Saskatchewan river in Canada to the southern headstreams of the Missouri, extending southward to the base of the Rocky mountains. The Blackfeet were roving buffalo hunters and accomplished warriors; by 1806, they already had large horse herds, many of which they had raided from tribes farther to the south. The Blackfeet also had strong trade relationships with British merchants of the Hudson’s Bay Company in Canada, exchanging valuable wolf and beaver pelts for guns, ammunition and alcohol. For twenty years, this trade relationship had worked to the Blackfeet’s advantage, enabling them to make war on their neighbors and dominate their Nez Perce and Shoshone rivals.
Lewis had no idea what a tense geopolitical situation he had stumbled into, but he did realize that his small party was in trouble. He attempted to approach to a mounted Blackfoot man, but the Blackfoot backed off in alarm. Not knowing how many Indians he was facing, Lewis feared the worst.
on his return to his party they all decended the hill and mounted their horses and advanced towards us leaving their horses behind them, we also advanced to meet them. I counted eight of them but still supposed that there were others concealed as there were several other horses saddled. I told the two men with me that I apprehended that these were the Minnetares of Fort de Prarie and from their known character I expected that we were to have some difficulty with them; that if they thought themselves sufficiently strong I was convinced they would attempt to rob us in which case be their numbers what they would I should resist to the last extremity prefering death to that of being deprived of my papers instruments and gun and desired that they would form the same resolution and be allert and on their guard.
After another tentative approach, the Indians halted and the two parties awkwardly shook hands. Lewis knew he was in an exceedingly vulnerable position, though he felt reassured when he realized there were only eight in the Indian party, concluding “I was convinced that we could mannage that number should they attempt any hostile measures.” Through halting sign language, he asked if there were any chiefs among them and dutifully handed out a flag, a Jefferson peace medal, and a handkerchief.
The Blackfeet invited Lewis and his men to camp at the base of some steep bluffs near “three solitary trees.” Despite nervousness on both sides, with Droulliard’s assistance Lewis talked with the men:
with the assistance of Drewyer I had much conversation with these people in the course of the evening. I learned from them that they were a part of a large band which lay encamped at present near the foot of the rocky mountains on the main branch of Maria’s river one ½ days march from our present encampment; that there was a whiteman with their band; that there was another large band of their nation hunting buffaloe near the broken mountains and were on there way to the mouth of Maria’s river where they would probably be in the course of a few days.
Emboldened, Lewis was determined to fulfill his diplomatic instructions to foster peace and further the interests of American trade. It was then that he made a near-fatal blunder. Having never encountered these people before, he had little idea of their trade advantage they held with the British in Canada, and he was unaware of their hostile relationship with other people of the plains. Lewis told the Blackfeet that he’d already secured the cooperation of the Nez Perce and the Shoshone for peace on the plains, in exchange for guns and other supplies.
I told these people that I had come a great way from the East up the large river which runs towards the rising sun, that I had been to the great waters where the sun sets and had seen a great many nations all of whom I had invited to come and trade with me on the rivers on this side of the mountains, that I had found most of them at war with their neighbours and had succeeded in restoring peace among them, that I was now on my way home and had left my party at the falls of the misouri with orders to decend that river to the entrance of Maria’s river and there wait my arrival and that I had come in surch of them in order to prevail on them to be at peace with their neighbours particularly those on the West side of the mountains and to engage them to come and trade with me when the establishment is made at the entrance of this river.
Lewis optimistically told himself that the Blackfeet men assented to his plan, and they may have given that impression, but the fact is the information he gave them made them alarmed, suspicious, and hostile. The Shoshone and the Nez Perce were the Blackfeet’s mortal enemies, and their territorial dominance relied on the Shoshone and Nez Perce not having rifles. What Lewis was proposing was a direct threat to their interests.
Hopeful that his overture had succeeded, Lewis offered the men horses and tobacco if they would come parley for peace. Receiving no reply, he established a watch so he and his men could get some sleep.
I took the first watch tonight and set up untill half after eleven; the indians by this time were all asleep, I roused up R. Fields and laid down myself; I directed Fields to watch the movements of the indians and if any of them left the camp to awake us all as I apprehended they would attampt to steal our horses. this being done I fell into a profound sleep and did not wake untill the noise of the men and indians awoke me a little after light in the morning.—

Two Medicine River in northern Montana, site of Lewis's deadly encounter with the Blackfeet. Courtesy of http://lewisandclarktrailwatch.blogspot.com/.
What he woke to was chaos. Exhausted, Joseph Field had laid aside his weapon; it was quickly and quietly taken by a Blackfoot warrior, along with the guns belonging to the sleeping Droulliard and Lewis. As the Blackfeet moved to escape, Field became aware of what was happening and quickly raised the alarm. His brother Reuben gave furious chase. He caught up to a young Blackfeet named Side Hill Calf and demanded the return of his brother’s gun. As the two men grappled for the weapon, Field plunged a knife into the Blackfeet’s chest, killing him dead.
Lewis woke when he heard George Droulliard shout, “Damn you, let go my gun.” An Indian was making off with Droulliard’s rifle and shot pouch; Lewis moved to help but found his own rifle missing. He drew his horse pistol and began to chase down the thief.
I ran at him with my pistol and bid him lay down my gun which he was in the act of doing when the Fieldses returned and drew up their guns to shoot him which I forbid as he did not appear to be about to make any resistance or commit any offensive act, he droped the gun and walked slowly off, I picked her up instantly, Drewyer having about this time recovered his gun and pouch asked me if he might not kill the fellow which I also forbid as the indian did not appear to wish to kill us.
Within moments, the thieves had been rounded up and the guns retrieved. Then Lewis saw to his horror that the Blackfeet were now attempting to steal their horses. Losing their horses would be a huge calamity, leaving his small band of men alone in hostile country with no means of escape. Hollering to his men to fire on the Indians if they would not stop, Lewis went after two men who had taken his horse.
at the distance of three hundred paces they entered one of those steep nitches in the bluff with the horses before them being nearly out of breath I could pursue no further, I called to them as I had done several times before that I would shoot them if they did not give me my horse and raised my gun, one of them jumped behind a rock and spoke to the other who turned around and stoped at the distance of 30 steps from me and I shot him through the belly, he fell to his knees and on his wright elbow from which position he partly raised himself up and fired at me, and turning himself about crawled in behind a rock which was a few feet from him. he overshot me, being bearheaded I felt the wind of his bullet very distinctly.
At this, the rest of the Indians fled. Lewis’s attempt at diplomacy had ended in death for two Blackfeet and near disaster for him and his men, leaving him shaken, scared, and furious. His horse was gone, but his men had managed to retrieve some of the others, along with several Indian horses that Blackfeet had left in their hasty retreat. Fearful that the Blackfeet would return, Lewis prepared for a quick departure, burning the shields, bows, and arrows the Indians had left and retrieving the American flag he had presented to the Blackfeet men. In his anger, he left the Jefferson peace medal about the neck of the dead warrior Side Hill Calf, “that they might be informed who we were.” He and his men then began a frantic flight back to the Missouri, covering 120 miles in two days, before a relieved reunion with the rest of the Corps of Discovery.
Lewis’s misadventure marked the first time blood was shed in a battle between a western tribe and a representative of the U.S. government. This incident, known as the Two Medicine fight, has often been cited as the cause of the Blackfeet’s subsequent hostile acts toward Americans, including the death of George Droulliard at Three Forks in 1810.
In reality, the causes were much more complex than a simple desire for revenge. An aggressive people, the Blackfeet were accustomed to losing men in battle, but the influx of American trappers up the Missouri in the years following the Lewis & Clark Expedition represented a threat to their military and economic dominance that they could not tolerate. As James Ronda writes in Lewis & Clark Among the Indians, “In the face of a massive assault on their plains empire, Blackfeet warriors hardly had time to think about avenging Side Hill Calf and his unfortunate companion. Lewis was unwittingly the prophet of events like the 1821 Immell-Jones massacre, he was not their cause. It was the more potent forces of guns and international trade that made the Blackfeet feared by a generation of American mountain men.”