The Commonwealth

The  is what is left of the pre-Great War American state of Massachusetts in New England. While traditionally called a Commonwealth in itself, before the Great War Massachusetts was also part of the New England Commonwealth of the United States in the alternate history of the Fallout universe. Most of it is a war-ravaged quagmire of violence and despair like much of the rest of the former United States (and perhaps the rest of the world), but it is also where the mysterious Institute is located.

Organizations
The Institute is likely the descendant of the Massachusetts Institute of Technology. Little is known about the Institute other than that the scientists working in the sealed environment possess highly advanced technology and technological skills. The Institute has created true artificial intelligence (AI) and is capable of manufacturing androids.

Another organization active in the Commonwealth, the Railroad, functions in direct opposition to the Institute, as their goal is to free sentient androids from their creators.

Harkness, Dr. Zimmer and Armitage are from the Commonwealth.

During the events of Broken Steel, Dr. Li leaves the Capital Wasteland on a trip to the Commonwealth, apparently to clear her head after the final activation of Project Purity.

Tobar, captain of the Duchess Gambit, made frequent trips to the Commonwealth when his ferry was in better condition.

Appearances
The is only mentioned in Fallout 3. According to Emil Pagliarulo, there are no current plans to visit it in Fallout 3 add-ons.

In the add-on The Pitt, Ashur mentions the Commonwealth in his speech to the slaves, stating that the Pitt is the envy of the Commonwealth.

Dr. Madison Li is absent from the Citadel following the events surrounding Project Purity. Rothchild comments that she has ventured north, in search of the Institute.

In the add-on Point Lookout, the Commonwealth was mentioned many times by different NPC's as the place they've been before or going to visit.

Related quests

 * The Replicated Man