Northern Commonwealth

The Northern Commonwealth was one of the thirteen commonwealths of the pre-War United States of America.

Background
Created in 1969, it was comprised of the former states of Montana, Wyoming, North Dakota and South Dakota. Both before and after the war, Highway 89 passes through the area and is used for travel. The commonwealth bordered the country of Canada and the Northwest, the Four States, the Plains, and Great Midwest Commonwealths.

Wyoming
Territories of Wyoming have been penetrated by Followers of the Apocalypse by the late 23rd century. Should the Great Khans be convinced to abandon the Mojave during the Second Battle of Hoover Dam, the region can become the crucible for a future Khan empire built in the northwest, bolstered by the ancient knowledge of governance, economics, and transportation obtained from the local Followers.

The plains can also host another tribe, the White Legs. If they are broken by Joshua Graham and the Dead Horses, they flee into the wilderness of Wyoming, where half their tribe dies in the first winter, with the remnants scattered to the winds the following spring.

Montana
Montana is home to various human communities with a thriving coal mining industry. If the Courier has the Lady Killer perk, it is revealed he may have had a child with a woman from there. Furthermore, the Brotherhood of Steel has a bunker in the region as well.

South Dakota
In Fallout 4, MacCready mentions a warehouse in South Dakota while searching warehouses in Goodneighbor. Mount Rushmore, a national memorial in South Dakota, is mentioned in the Pioneer Scout archaeologist exam, and the Atomic Command video game.

Appearances
The Northern Commonwealth is mentioned only in Fallout 3, and Fallout: New Vegas and its add-on Honest Hearts. South Dakota's Mount Rushmore appears in the Atomic Command game in Fallout 4 and is mentioned in the Fallout 76 Wild Appalachia update.