The 37s is the name for the Vault Dwellers formerly of Vault 37. Located to the north of the city, it was set to open after 125 years. Upon opening it successfully established a settlement, using the Vault itself as a base. They would come into constant conflict with the outsiders of the Wasteland, who were paranoid about Vault dwellers because of their experience with the dwellers of Vault 36.
Experiment
Set to open 25 years after Vault 36, the two experiments were linked. Vault 37 was meant to emulate the political and colonial staff arriving to the planet to take over from the first military and scientific figures who had established it. Vault 37 dwellers were not given many armaments and were told they could probably trust the outsiders when their vault open. They were given advanced scientific knowledge for machinery and techniques that weren't shared with the 36s. It was expected that Vault 36 would have established control over the area, pushed out the few primitive survivors and the 37ers would take over the leadership role while the 36ers enforced their will.
Opening the Vault
The 36s had already been defeated 19 years prior. People remembered their violence though and the dwellers of 37 were attacked on sight. Their initial scouting teams were either killed or taken prisoner. The dwellers then emerged with a larger force, armed with weapons from the security armory and improvised devices created from scientific equipment. With this gear they were a formidable opponent and captured some wastelanders. They were interrogated and the 37s learned about the Wastelanders hatred for Vault dwellers. Realizing they were facing a totally hostile world, the Vault Dwellers adopted a policy of isolation. They kept the location of their vault hidden for many years, only sending out small teams to scavenge for necessary technology. The lower levels of the vault were turned into a massive green house using UV arrays from a destroyed tanning salon and equipment from their GECK. After a decade of growing their strength and raiding, they emerged from the Vault to conquer the surrounding areas. Wastelanders were pushed out and were shot on sight. The wastelanders prepared for another war, but when the 37s didn't expand and kept to themselves they were tolerated. On occasions groups have tried to raid or even invade their territory. In 2228 an army of raiders invaded and were decisively defeated.
Present Day
37s control a small amount of territory with some farms and small settlements. Heavily militarized and paranoid of all outsiders, they will sell electricity and purify water in return for a 20% cut of it. RadRunners offered them replacement technology for some of their Vault-Tec gear and they are the only caravan in the wastes which can freely come and go, others must wait outside at a small trade outpost which is deliberately inhospitable to discourage long stays. Most of the rest of the wasteland has learned to tolerate them and they are so isolated they aren't much of an issue. They also will trade the use of their rare functioning auto-docs in return for fertile women to be inducted into their society. Their small population pool makes the possibility of incest a great concern, as there were only a around a thousand Vault Dwellers inside Vault 37.