I'm not sure about the Texas division, but Fallout 3, Fallout New Vegas, and Fallout 4 all mention or allude to the existence of at least one chapter of the Midwestern division, which would bring our total up to five chapters, possibly more. So all in all, we have at least one chapter on the west coast and at least one chapter on the east coast, potentially as many as four. The Eastern division wishes to control pre War technology in order to prevent humanity from repeating the mistakes of the past - such as another Great War.

The Eastern division is distinguished from the Western division in a number of ways, in that the Eastern division's philosophy has been expanded to support the recruitment and indoctrination of 'civilian' outsiders and also to eliminate threats to humankind such as feral ghouls, super mutants, synths, and other abominations created by the misuse of technology. Both the Capital Wasteland and Commonwealth chapters (or rather garrisons) appear to be headed by a Sentinel appointed by Arthur Maxson, who campaigns up and down the east coast in his airship the Prydwen. At best, it is the dominant military force in the Commonwealth. At worst, it has been destroyed along with the majority of the Eastern division's forces. The ultimate fate of the Commonwealth chapter is unknown as it is dependent on the outcome of Fallout 4. We also have the Commonwealth chapter based out of Boston Airport and the Cambridge Police Station.

In any case, the main 'chapter' is the Capital Wasteland chapter headquartered at the Citadel, Project Purity, and Adams AFB. As of 2287 there are two 'chapters' in the Eastern division, although it should be known that power is much more consolidated and centralized in the Eastern division such that the term 'chapter' is more loosely applicable than it would be with the Western division. This one is headed up by Arther Maxson, descended from Roger Maxson who originally founded the Brotherhood of Steel on the west coast. We also have the Eastern division, which I would consider to be the larger and more successful of the two main divisions as of 2287.

This philosophy is taken to such an extreme that it is hard to consider the Western division to be anything other than overzealous, which is the major reason that they are so disliked by the average wastelander. In all cases, the Western division continues to prioritize the preservation of pre War technology - particularly weaponry - above all else and works to barr anyone else from 'misusing' it. It could be completely gone, it could exist in an uneasy truce with the NCR, or it could even be one of the major powers in an independent New Vegas. The fate of the Mojave chapter is also unknown, as it is dependent on the outcome of Fallout New Vegas. At worst, the two are still at war and the Lost Hills chapter is still bunkered up underground. The Western division's current relationship with the NCR is left vague. A cult of personality seems to have developed around Arthur Maxson (who is ironically on the other side of the wasteland and no one has personally met, except for maybe when he was an infant) and he has been semi-deified by some. We know that as of 2287 the Lost Hills chapter still exists and maintains a power structure comprised of a council of elders. Other than that its the Devs' choice reallyД®xcluding the Midwest or Texas divisions? Well, we have the Western division - two known chapters, those being the main one headquartered in New California (presumably at Lost Hills) and the Mojave chapter. C) You have minor chapters whose existence is debated or left unclear, mainly the Mojave chapter, The Montana bunker, Chicago chapter, and whoever it is that Caesar's legion fought. B) You have the eastern division under Maxson, which might be (depending on how you end FO4) the strongest BoS chapter out there, projecting their power across the entire east coast, they are kinda the Constantinople to Lost Hills' Rome. It is safe to say however that : A) The California chapter is still operating out of lost hills, they are in contact with Maxson and have more than just the Lost Hills bunker, since the NCR is said to have destroyed at least 5 bunkers in Cali I think, and in FO4 the BoS is supposedly purging Maxson worship from smaller chapters. Well, the real answer here is there are as many as the devs want, so far the BoS was present in every single FO game, and it seems to me like the BoS itself is kinda having a hard time keeping count of all their people.

Brotherhood of steel chapters