Commonwealths

The thirteen commonwealths of the United States were created in 1969, as a new level of governance between the state and federal governments. In Massacussetts, the foundation of the Thirteen Commonwealths resulted in the discontinuation of the use of the local State House. States and commonwealths were both used to describe regions and governmental entities before and after the Great War. In Appalachia, federal documents use the distinction "Territory of Appalachia."

Confirmed commonwealths
There are a total of thirteen commonwealths covering the United States of America. Although all thirteen were outlined by J.E. Sawyer in his Fallout RPG project (see below), only the following have been mentioned in released games:
 * Great Midwest Commonwealth, containing the state of Illinois.
 * Southwest Commonwealth, containing the state of Nevada.

Another one was mentioned in merchandise, which is of unclear canonicity:
 * Columbia Commonwealth, containing the state of Virginia.

Behind the scenes

 * The idea of dividing the United States into thirteen commonwealths originated during Fallout's development (1997). According to Tim Cain, Leonard Boyarsky didn't want to use the regular 50-star flag and used the 13-star design because "it looked cool", and planned to explain it as it being divided into 13 super-states, but the explanation never materialized.
 * The commonwealths were planned to be expanded on in Van Buren. The tech demo includes an U.S. soldier serving in a division of the Great Midwest Commonwealth (2003). Following its cancellation, Joshua Sawyer published a breakdown of the commonwealths and their constituent states in his unofficial RPG (2004), explaining that the commonwealths were an intermediate level of political organization created in the early 21st century to help create legislation broad enough to benefit those states with common regional concerns, but narrow enough not to affect those states with dissimilar interests or political cultures. The reality refused to conform, as the commonwealths did everything to promote their own interests at the expense of other commonwealths, not to mention the internal squabbles between states constituting the individual commonwealths. The breakdown was as follows:
 * Columbia Commonwealth, comprised of the states of Maryland, the District of Columbia, and Virginia.
 * East Central Commonwealth, comprised of the states of Ohio, Kentucky, and Tennessee.
 * The Eastern Commonwealth, comprised of the states of New York, Pennsylvania, New Jersey, Delaware, and West Virginia.
 * Four States Commonwealth, comprised of the states of Utah, Colorado, Arizona, and New Mexico.
 * Great Midwest Commonwealth, comprised of the states of Minnesota, Wisconsin, Michigan, Illinois, and Indiana.
 * Gulf Commonwealth, comprised of the states of Louisiana, Mississippi, Alabama, and Florida.
 * New England Commonwealth, comprised of the states of Maine, New Hampshire, Vermont, Massachusetts, Connecticut, and Rhode Island.
 * Northern Commonwealth, comprised of the states of Montana, North Dakota, Wyoming, and South Dakota.
 * Northwest Commonwealth, comprised of the states of Alaska, Washington, Oregon, and Idaho, and the northern half of California.
 * Plains Commonwealth, comprised of the states of Iowa, Nebraska, Missouri, Kansas, and Oklahoma.
 * Southeast Commonwealth, comprised of the states of North Carolina, South Carolina, and Georgia.
 * Southwest Commonwealth, comprised of the states of Nevada and Hawaii, and the southern half of California.
 * Texas Commonwealth, comprised of the states of Texas and Arkansas.
 * Although indirectly mentioned in every Fallout game due to the use of the 13-star flag, Commonwealths were first explicitly mentioned in Fallout: New Vegas (2010), with the Great Midwest Commonwealth and the Southwest Commonwealth confirmed. In Fallout 4 (2015), the commonwealth foundation date was established as 1969, which differs from the "early twenty-first century" date of establishment from Joshua Sawyer's unofficial RPG.