Location The locations in the post - nuclear United States form the backdrop in which the events of the " Fallout " series occur . Many have diverse environments where anything can happen , such as a special encounter , or just a skirmish with raiders . The environments and places have been changed over the course of the many games , as the settings have always been in different places , and always brought new surprises with them . Settlements . Capital Wasteland . In the Capital Wasteland , there are 22 settlements , ranging in size from Rivet City , with a population of 43 named characters and 7 Stores , to Girdershade : 2 people and no merchants . Apart from Rivet City , there are 4 other major settlements : Megaton , which would be probably the first settlement the Lone Wanderer encounters after escaping the vault ; Underworld , the city inside downtown DC full of ghouls ; Tenpenny Tower , a former luxury hotel that Allistair Tenpenny lets people in for the right price - ghouls need not apply ; and the Citadel , home of the Brotherhood of Steel . Besides those , there is the Republic of Dave , Canterbury Commons , Oasis , Paradise Falls , the Temple of the Union , Little Lamplight , Arefu , Andale , and the Reilly ' s Rangers compound are all settlements of a medium size , and all have related quests . Vault 101 and 112 both are also populated : Vault 101 is where the story starts , yet is closed after being left for the first time , is reopened during the Trouble on the Homefront quest , and after that , it is once again sealed , but this time for good . However there is evidence of an inevitable rebellion as Butch is found in Rivet City in the Muddy Rudder . Vault 112 , home of the Tranquility Lane simulator , is populated only by RoboBrains and , briefly , the Lone wanderer ' s father , James . Mojave Wasteland . In the Mojave , many different settlements can be found throughout the land , either run by a particular faction or operating independently . Some of these independent settlements include Goodsprings , Primm , Novac , Nipton , Westside , & North Vegas Square . The New California Republic controls a majority of the Mojave & various habitable settlements by the start of the game , including the various Ranger stations , the Mojave Outpost , HELIOS One , Boulder City , Camp Golf , Camp Guardian , Camp McCarran , Camp Forlorn Hope , Sloan , Aerotech Office Park , Bitter Springs , & Hoover Dam . Caesar ' s Legion , who have begun to push westward to challenge the NCR , has taken the Fort as Caesar ' s base of operations , as well as Cottonwood Cove & the town of Nelson as footholds across the Colorado River . New Vegas , specifically the Strip , is primarily operated by Mr . House , while the Kings are the de - facto rulers of Freeside . Additionally , smaller factions have developed their own settlements throughout the Mojave . After their escape from Vault 34 , the Boomers settled down in Nellis Air Force Base , using their artillery strikes to steer outsiders away . After losing HELIOS One to the NCR , the remaining members of the Mojave Chapter of the Brotherhood of Steel have retreated back to their underground bunker of Hidden Valley . After staging an audacious breakout , a gang of NCR convicts known as the Powder Gangers have taken the NCR Correctional Facility as their base of operations , while a splinter group traveled through the Mojave & settled down in Vault 19 . After the massacre at Bitter Springs , the remaining members of the Great Khans have relocated westward towards Red Rock Canyon . While traveling through the western United States after the fall of the Master , a group of super mutants & nightkin led by Marcus eventually settled down in Black Mountain until a group led by one of the mutants , Tabitha , drives Marcus ' s group away & eventually created the State of Utobitha on Black Mountain , while Marcus ' s group eventually discovers an abandoned ski lodge to the west of New Vegas & creates Jacobstown as a safe haven for super mutants & nightkin . The Island . On the Island , there are a total of 4 non - player settlements , with 4 buildable settlements that can be created by the Sole Survivor . The majority of people living on the island live in Far Harbor , the only remaining settlement not taken over by the Fog , while DiMA and his escaped synths live up in the wind farm known as Acadia , and the Children of Atom have resided in the radioactive submarine base known as the Nucleus . Additionally , a community of Pre - War celebrities who ' ve voluntarily transplanted their brains into Robobrains reside in Vault 118 found underneath Cliff ' s Edge Hotel . As well , there are 4 buildable settlements on the Island that the Sole Survivor can build on but can only be built on after completely certain quests from the people of Far Harbor : Dalton Farm , Echo Lake Lumber , National Park Visitor ' s Center , & Longfellow ' s cabin . Nuka - World . In Nuka - World , the raiders and their slaves reside in Nuka - Town USA , with the Pack residing in the Bradberton Amphitheater , the Operators residing in the Parlor , and the Disciples residing underneath Fizztop Mountain , with trade being established in the Nuka - Town Market . Additionally , a buildable settlement can be created on the outskirts of Nuka - World at the Nuka - World Red Rocket , but only once power has been restored to Nuka - World . Vaults . There were a total of 122 Vaults that were known to the public , and this number may not include any of the secret Vaults that the pre - War American government could have constructed for private purposes of protecting high - ranking officials . Most of the Vaults were actually created for testing some sort of social , or emotional flaw and how they would react to it , and only about 17 of the Vaults were actually meant for people to live normal lives in the Vault , and not to be exposed to carnivorous plants ( Vault 22 ) , or the door not meant to close all the way , thus exposing the residents to lethal amounts of radiation ( Vault 12 ) .