In 1836 Pierre Choteau Jr. commissioned a third steamboat for the American Fur Company, the St. Peter's, a 119-ton side-wheeler. This ship would be the transmission vector for one of the worst outbreaks of Small Pox amongst the Indians. The impact of the disease was made far worse by well-meaning whites who attempted primitive inoculations, compounded by ignorance, misunderstanding and poor hygiene.
The ship set out on it's maiden voyage in the spring of 1837. Before the ship arrived at Fort Leavenworth on about April 29, one of the deckhands became sick with a fever. A few days later while in the vicinity of the Black Snake Hills it was suggested to the captain that the sick man be put ashore, however the captain was unwilling to condemn the ill man to starvation in the wilderness. By the time the ship had arrived at Council Bluffs, it was apparent that the crewman was infected with Small Pox. By this time several others on the ship were showing symptoms as well. At Council Bluffs three Arikara women boarded the vessel and soon also became ill.
The infected ship continued on its scheduled journey upriver. The Indians were expecting the goods and merchandise carried by the ship, and Company officials on the ship anticipated that the Indians would be hurt and angry if the ship didn't arrive. They also harbored the misguided hope that the disease could be contained on the ship. Lack of communications with company superiors in St. Louis compounded these errors in judgment.
The St. Peter's made a brief stop at Fort Pierre, where Jacob Halsey, a company clerk was taken on board, bound for Fort Union. Halsey soon came down with Small Pox. He had been vaccinated, and did make a recovery, however for a period of time he too was able to spread the infectious disease.
On June 18th 1837, the St. Peter's arrived at Fort Clark, near the Mandan villages. Francis Chardon was the bourgeois at this fort. The ship remained there three days before departing for Fort Union.
By the time the St. Peter's arrived at Fort Union, several of the deck hands had died of the disease. On arrival only Jacob Halsey was showing visible signs of the disease. In an effort to contain the disease at Fort Union, primitive inoculations were attempted by fort personnel. Puss from Halsey's skin eruptions was used to inoculate about thirty Indian women who were living in and around the fort as wives and companions of trappers. The results were absolutely devastating and only served to further spread the disease. Within about two weeks those who had received the inoculations began to die in a most horrible manner. According to Larpenteur (in Forty Years a Fur Trader), one of the fort's personnel, "It was awful-the scene at the fort, where some went crazy, and others were half eaten up by maggots before they died." Larpenteur's description of events taking place just prior to and during the epidemic can be read here.
While the epidemic was at its peak a group of about 40 Indians attempted to visit the fort. The forts doors were locked against them, but they wouldn't leave until they were shown a boy covered in scabs. Larpenteur claimed the only exposure of these Indians was to the boy. Even so, more than half of this group would eventually die of Small Pox.
Back at Fort Clark, Chardon does not record when he first became aware that men on the St. Peter's had Small Pox, but he did send out messages warning the Indians to stay away from his establishment. The Indians came anyway, convinced they were being mislead to deny them access to trade goods. Meanwhile the three Arikara women had left the boat and gone to join their tribe, which had moved in amongst a group of Mandans and Gros Ventres. Although these women were recovering from the disease, they were still infectious.
On July 14th, less than a month after the St. Peter's passed through at Fort Clark, the first Indian, a young Mandan died. From then on Chardon kept a tally of the death toll, five, six, ten, fifteen a day, chiefs and friends and in-laws amongst the toll. On August 11th he ended his tally, writing "I keep no a/c of the dead, as they die so fast that it is impossible." He recorded stories of Indians committing suicide to escape the miserable death brought on by disease, of husbands and wives killing themselves, of parents killing their children and then themselves. On August 31st he estimate the toll amongst the Mandans at five hundred, later he revised that to eight hundred. Chardon's two year old son died of Small Pox on September 22. By October the spread of the disease appeared to be slowing, but Chardon continued to note scattered deaths for several months.
At Fort Union the effects of the disease were equally as destructive. Even during height of the epidemic bands of Assiniboines continued to arrive at the fort to trade. Halsey reported the following, "I sent our interpreter to meet them on every occasion, who represented our situation to them and requested them to return immediately from whence they came however all our endeavors proved fruitless, I could not prevent them from camping round the Fort-they have caught the disease, notwithstanding I have never allowed an Indian to enter the Fort, or any communication between them & the Sick; but I presume the air was infected with it for a half mile... I do not know how many Assiniboins have already died as they have long since given up counting but I presume at least 800 and of the Blackfeet at least 700, it was introduced to that nation by a Pied noirs who embarked on the St. Peters at Little Missouri. The Mandans have all died except 13 young & 19 old men."
The disease was also introduced among some of the Sioux bands around Fort Pierre when the St. Peter's stopped there and distributed government annuity goods.
Surprisingly, after the epidemic died out in the winter of 1837-1838, most of the tribes did not become hostile to the whites. Some Indians were so emotionally overwhelmed by the destructive power of epidemic as to beg the white traders not to desert them.