"Make 'em look up, not down."

The Treehouse is a location at the southern end of the commonwealth.

The original origin of The Treehouse was that it was used for spies during the war, in which it could hold up to 2 spies, but only one bed. once the bombs fell, they fleed the place, and since only those two were the only ones who knew about it, it stayed hidden. Timeskip to about 210 year later, once Whisper and Alan are out and wandering the wasteland, they do the tasks for Edward Deegan and Jack Cabot. During the raid of the Assylum, Deegan gets injured, and Whisper and Alan agree that Whisper takes him to safety while Alan finishes the mission. At this time, Deegan had a hard time walking, and so Whisper went to search for a place to help him recover. The dumbass found The Treehouse by sitting down on the tree trunk to rest and sat on the handle.

The Treehouses original use was a place for Whisper to watch over Deegan while he recovered, for the most part only Whisper and Deegan stayed in there, with Alan coming and visiting ocassionally. Once Deegan started to heal and feel better, Whisper decided that he wanted to build onto it and make it into a place minorities, specifically ghouls, could stay and feel safe. Whisper decided to get his friend Mel to help, with his robot SONYA2. with Mels help Whisper was able to make it into a very big area for people to stay. 

Red dot is the location around where it'd be:

The mission and purpose is just so there's a place for ghouls and other minorities to stay. It's used as a reminder to the ones on the outside that there's someone out there who cares about them and is fighting for them and their rights. Whisper hopes to help as many as he can.

The Treehouse values respect and love from everyone living there. There aren't too many values other than hoping for the hate towards groups like Ghouls and Synths to end, and to respect them as people.

It's really not a super complex recruitment process, though Whisper has to be the one to let them in. Other members can ask about letting others stay, in which Whisper will introduce himself to them, and usually met up with them a few times to make sure they can be trusted. Usually Whisper looks into their background to make sure they're not part of any other hate group such as the BOS or a Raider. It really just depends on if Whisper likes you or not.

The main and only Headquarters is placed on the southern end of the Commonwealth. The Treehouse is disguised to look like a tree trunk, hence the misleading, but still technically accurate name, "The Treehouse."  Whisper purposely named it that to trick outsiders to look up for a  place in the trees, rather than down at the trunk. The top of the trunk  lifts up to reveal a ladder that goes down to the actual location. The  inside of The Treehouse is actually quite big, holding a few people, who  live there full time. It can hold up to 10 people, but Whisper can add  more rooms if needed. There's also a Kitchen / dining area, a living  room / hanging space, a bar, a janitors closet, and everyone has their  own bathrooms within their rooms.

The public opinion of The Treehouse depends on what kind of person you are.

General Public:
For the most part, the general public who know about its existence don't really have an opinion on it, they just don't really care. There'll be the occasional person who wants to go and look for it, but to no luck, since no one has any idea where even the general area of the location even is, and no one knows who the leader is either. The General ghoul population like to hear about them, its a comforting thought to them that there's someone and somewhere out there that cares about them.

Railroad:
The Railroad are actually on good terms with The Treehouse, due to Whisper being a member of The Railroad. Whisper lets The Railroad send over synths in need of a temporary place to stay, and Whisper does the same when he finds synths in need of help from The Railroad.

Minutemen:
The Minutemen don't exactly have an opinion, they think it's a good cause, but that's about it.

Brotherhood Of Steel:
The Brotherhood basically hate The Treehouse, but don't exactly see them as a threat.