Did the Assiniboine live around Fort Assiniboine (Canada)?

According to the wikipedia entry in the question, there are some Assiniboines living in Alberta as well.

After a fair bit more digging, I found that there's a closely related group that is either an isolated set of bands of Assiniboines or separate tribal group, depending on who you ask. Their languages, while still Siouxan, do not appear to be mutually-intelligable with other Assiniboines. Wikipedia has them under Nakoda (Stoney). They do in fact hail from central Alberta.

Many bands of Stoney go by alternate names that include "Assiniboine". For example, the mountain bands are sometimes referred to as "Strong Wood" or "Thickwood" Assiniboine. Their present-day reservation is in Alberta about halfway between Calgary and Banff, which is today only about a 6 hour drive south of Ft. Assiniboine.

There are a lot of definition issues here:

• Peoples are not a clear-cut and stable notion. Though you can define at a given time who is part of a tribe or nation, such groups evolve; individuals get born, live and die, meaning that the group membership necessarily changes, and forces you to revisit your definition constantly. The Wikipedia page indicates that the Assiniboine people are the result of a split which occurred around 1640, i.e. quite recently.

• Such group evolution was especially fast for North American Indians in the Great Plains, from the 17th century onward. This is due to the introduction, from Europe, of two crucial innovations: guns and horses (Jared Diamond would add germs here, which altered the demographic situation to a great extent). These innovations allowed the development of the iconic mounted hunter/warrior who chases buffaloes; that culture was new and flourished for at most two centuries before being mostly killed off by the quasi-extinction of the buffalo, and the appropriation of land by agriculture-minded settlers.

• Being a semi-nomadic culture with no agriculture, the Assiniboine could not be pinpointed to a well-defined territory. Over the decades, the Assiniboine groups roamed a lot. In the map you show, the "Assiniboine" area is not defined as "these parts of land are owned by the Assiniboine", but rather as "in this area you may meet some Assiniboine, or not, depending on your luck, and you may meet non-Assiniboine as well".

• The normal large-scale political structure of North American Indians was the rather fluid notion of "confederations", in which groups associated more or less closely, with a lot of interactions in all directions. They never had the kind of hard border that nation-states produced in post-medieval Europe. Even if you could define a specific group as "true Assiniboine", then it would be surrounded by a continuum of other groups which would represent the whole range from "99% Assiniboine" to "1% Assiniboine and 99% something else".

• The "Assiniboine" name is external; it comes from Ojibwe and means something like "stone enemy" (see this). The Assiniboine were certainly not naming themselves that way. Ethnologists have tried to classify Indian groups through linguistics, resulting in several conflicting classifications. The Assiniboine "properly said" (with all the fuzziness described above) would be the Nakhóta (or Nakhóda), a name that also applies to the Stoney, though the latter speak a distinct language. Compounding the issue is that the Stoney can be defined as a split from the Assiniboine (around mid-18th century) and comprise several subgroups, one of them being called the "Plains Assiniboine".

• Today's tribe names and compositions are, in great part, the result of the imposition of European concepts of nations, territories and polities; and the ultimate demise of the Indian nations at the end of the 19th century implied sedentism and the cessation of inter-group warfare. Tribe naming after that date can be deemed to be a legal and fiscal concept, quite removed from the previous notions by which the Indian groups named and recognized themselves.

With all the caveats explained above, Fort Assiniboine was founded in 1823 (under the name "Athabaska River House" -- the renaming occurred at some unspecified date around mid-19th century). At that time, the area was on the edge of the influence zone of a loose group of tribes who, by the European classifications used at that time, were designated as "Assiniboine". Their vast "territory", stretching from modern Alberta to North Dakota, was considered to be under their control because they were the groups that traders dealt with; but at their demographic height they were only 10000 or so, which illustrates the limits of the concepts of control and territory.