Commonwealths

The thirteen commonwealths of the United States were created in 1969, as a new division of government. Both state and commonwealth names were used to describe regions and governmental entities before and after the Great War. In Massachusetts, the foundation of the Thirteen Commonwealths resulted in the discontinuation of the use of the local State House. 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. Only the following two have been mentioned in released, canon games.

Great Midwest Commonwealth

 * ED-E's pre-War Illinois license plate reads "Great Midwest" across the top.

Southwest Commonwealth

 * The commonwealth name is seen on the Red Rock Canyon stone marker and Nevada state flag.
 * The bumper sword's pre-War Nevada license plate reads "Southwest" across the top.

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 did not wish to use the regular 50-star flag and instead 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 (2003) includes an U.S. soldier serving in a division of the Great Midwest Commonwealth. 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, made up of the states of Maryland, the District of Columbia and Virginia.
 * East Central Commonwealth, made up of the states of Ohio, Kentucky and Tennessee.
 * Eastern Commonwealth, made up of the states of New York, Pennsylvania, New Jersey, Delaware and West Virginia.
 * Four States Commonwealth, made up of the states of Utah, Colorado, Arizona and New Mexico.
 * Great Midwest Commonwealth, made up of the states of Minnesota, Wisconsin, Michigan, Illinois and Indiana.
 * Gulf Commonwealth, made up of the states of Louisiana, Mississippi, Alabama and Florida.
 * New England Commonwealth, made up of the states of Maine, New Hampshire, Vermont, Massachusetts, Connecticut and Rhode Island.
 * Northern Commonwealth, made up of the states of Montana, North Dakota, Wyoming and South Dakota.
 * Northwest Commonwealth, made up of the states of Alaska, Washington, Oregon and Idaho, and the northern half of California.
 * Plains Commonwealth, made up of the states of Iowa, Nebraska, Missouri, Kansas and Oklahoma.
 * Southeast Commonwealth, made up of the states of North Carolina, South Carolina and Georgia.
 * Southwest Commonwealth, made up of the states of Nevada, Hawaii and the southern half of California.
 * Texas Commonwealth, made up 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 being named in-game. 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.
 * The Columbia Commonwealth is also mentioned on official Bethesda store merchandise, within a certificate of ownership for a Nuka-Cola delivery truck.