|The following is based on Van Buren and has not been confirmed by canon sources.|
The Blackfoot tribe are unrelated to the native American tribe of the same name. They were "founded" by a former military group (led by a Captain John Bloch) which was left stranded after its HQ and transport vehicles were destroyed in the War. Skilled with weapons but lacking the knowledge of how to farm, Bloch's group fell into raiding. During a standoff in one raid on a small ranching community the ranchers called a truce and offered to pay the raiders "protection money" to keep them from raiding. The raiders agreed and that became the start of a successful relationship. As the raiders had few places to spend the money they ended up spending it on equipment, food, and liquor from the ranchers, and the two groups became intermingled over the next decade as disaffected rancher sons went to join the raiders and older raiders "retired" to start ranching. During this time several wandering groups of Native Americans (who left their reservations after the American government collapsed and there was no longer anything to stop them from claiming nearby land) established a relationship with the raiders/ranchers and the two groups joined together for greater strength; the tribes gain access to some technology and a fortified home, while the raiders/ranchers gained access to skilled outdoorsmen who knew the area very well. A great fire destroyed much of their original settlement and they ended up relocating to a small tourist trap in the hills. They continued to raise their Brahmin and make extensive raids into other communities for livestock and supplies. Their firearms succumbed to dirt and wear and over time they forgot how to repair and maintain them, becoming much like any other tribe.
About 20 years later a sickness depleted their available number of younger people, so they took to raiding other tribes for children and teens in order to replenish their numbers. Eventually this scope broadened into slaving for laborers as well as adoptees, and slaving for profit soon followed. Now they are slave-raiders with a fixed base, despised by all others near them for their predation.
Brahmin and slaves. With the Prisoner's help, maybe bullets and simple guns as well, which would also increase their need for junk and slag parts.
Interactions with other locations
The Blackfoots are mostly parasitic, taking things from other tribes and settlements. However, they export slaves to Caesar's Legion and other tribes and when their herds are doing well they sell Brahmin products to nearby communities (including places they don't sell slaves to, or to caravans). If the player can revitalize their weapon production, they might start exporting pipe rifles, zip guns, bullets, or even actual simple firearms if things go well.
The Blackfoots have no interest in ghouls (they consider them walking dead and bad spirits!) or super mutants (demons in the flesh of men!) and will be very unwelcoming of such beings within their town, requiring a lot of diplomacy or gifts to win them over.