living in two north-south tribal groups; one, the so-called Fall Indians (Canadian or northern group) of 260 lodges (≈2,500 population) traded with the North West Company on the Saskatchewan River and roamed between the Missouri and Bow Rivers. They were active in southern Alberta through the late 1800s, but were based near present-day Fort Belknap, Montana by 1862 when Jesuit missionaries arrived there. The U.S. and Canadian governments sought to keep nomadic peoples from crossing the border, and the Americans opened an Indian agency to supply the Gros Ventre with aid at Fort Belknap first from 1871-1876, and permanently in 1878, with a reservation there being established in 1881. The Kutenai migrated westwards out of Alberta, possibly in the early eighteenth century, but still occasionally ventured into the Bow River region to hunt bison by the time of European contact. As well, people from other ethnic groups, such the Métis and Iroquois occasionally intermarried with local peoples and were adopted into existing bands or created their own new bands of mixed heritage. An example is the Michel Band from the Calahoo area, many of whom are descended from William Callihoo, an Iroquois or Métis fur trader from the east who married one or more local Cree women and founded the band. Plains peoples were able to congregate into larger communities often when following large buffalo herds and had more complex political structures than Subarctic peoples who had to remain dispersed to find enough food (even centuries later there are more First Nations band governments in the north, but the fewer southern communities are much more populous). A group of bands united into a semi-permanent alliance for common defence was called a confederacy by non-Native observers. Such confederacies were often multi-ethnic in that they included bands from a number of tribes. The two key confederacies in what later became central and southern Alberta during the eighteenth and nineteenth centuries were the Blackfoot Confederacy (consisting of bands from the Piegan, Kainai, Sikisika nations, later joined by the Tsuu T'ina and, for a time, Gros Ventre) and the Iron Confederacy (bands of Plains Cree, Assiniboine, and Saulteaux, and Stoney). Initially on friendly terms, these two grouping eventually become long-term enemies (the Battle River was named for conflict between the two groups that happened near it approximately 1810, around the beginning of their hostilities) until the Battle of the Belly River on October 25,