dead, as they die so fast it is impossible," and by the end of the month, "the Mandan are all cut off except twenty-three young and old men." Once the disease reached Fort Union, there was an effort to prevent its spread, but it would eventually decimate the Assiniboine. Daschuk, Dollar, and Ray all find that there was an effort to keep returning fur traders from entering the fort, but as Dollar finds, returning traders began to get quite aggressive until they were shown an infected boy, as they left they took the disease with them. Halsey wrote, "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..." Later, a longboat was sent to Fort McKenzie via the Marias River. At Fort McKenzie the disease spread among the Blackfoot people housed there. The epidemic continued to spread into the Great Plains, killing many thousands between 1837 and 1840. In the end, it is estimated that two-thirds of the Blackfoot population died, along with half of the Assiniboine and Arikara, a third of the Crow, and a quarter of the Pawnee. A trader at Fort Union reported "such a stench in the fort that it could be smelt at a distance of 300 yards", as the bodies were buried in large pits, or tossed into the river, which would have likely contributed to continued infection as the bodies remained infectious after death. There were three major vaccination attempts to stop the spread of smallpox when the epidemic began. Many traders tried to obtain vaccines from the American Fur Company but it was unwilling to heed their requests. The American government made some efforts under the Indian Vaccination Act of 1832. Some did receive vaccines for smallpox, typically ones that were in contact with White Americans, usually in the southern United States. However, the Office of Indian Affairs did not have the network or information needed to vaccinate the plains people quickly, nor did they try establish the needed network. The Hudson Bay Company