Commonwealth is a designation used by four of the 50 states of the United States in their full official state names: Kentucky,  Massachusetts,  Pennsylvania,  and Virginia.  Commonwealth is a traditional English term for a political community founded for the common good. Prior to the formation of the United States of America in 1776, all four were part of Great Britain's possessions along the Atlantic coast of North America. As such, they share a strong influence of English common law in some of their laws and institutions.  
of the United States
The term commonwealth does not describe or provide for any specific political status or legal relationship when used by a state.  Those that do use it are equal to those that do not. A traditional English term for a political community founded for the common good, it is used symbolically to emphasize that these states have a "government based on the common consent of the people"  as opposed to one legitimized through their earlier colonial status that was derived from the British crown. It refers to the common "wealth", or welfare, of the public  and is derived from a loose translation of the Latin term res publica. [a]
Besides the four aforementioned states, other states have also on occasion used the term commonwealth to refer to themselves:
- The term commonwealth is used interchangeably with the term state in the Constitution of Vermont. 
- Delaware was primarily referred to as a "state" in its 1776 Constitution; however, the term commonwealth was also used in one of its articles. 
Two U.S. territories are also designated as commonwealths: Puerto Rico and the Northern Mariana Islands. When used in connection with areas under U.S. sovereignty that are not states, the term broadly describes an area that is self-governing under a constitution of its own adoption and whose right of self-government will not be unilaterally withdrawn by the United States Congress. 
On September 28, 1786, the residents of Kentucky County began petitioning the Virginia legislature for permission to become a "free and independent state, to be known by the name of the Commonwealth of Kentucky".  On June 1, 1792, Kentucky County officially became a state. As in Virginia, the official title of the elected local prosecutor in each of Kentucky's political subdivisions is the Commonwealth's Attorney, as opposed to State's Attorney in other States or the more standard District Attorney. Kentucky is the only state outside of the original Thirteen Colonies that uses commonwealth in its name.
Massachusetts is officially named The Commonwealth of Massachusetts by its constitution. The name State of Massachusetts Bay was used in all acts and resolves up to 1780 and in the first draft of the constitution. The current name can be traced to the second draft of the state constitution, which was written by John Adams and ratified in 1780. 
In Massachusetts, the term State is occasionally used in an official manner, usually in a compound structure rather than as a standalone noun. This is evident in the names of the Massachusetts State Police, the Massachusetts State House, and the Bridgewater State Hospital.
The Seal of Pennsylvania does not use the term, but legal processes are in the name of the Commonwealth, and it is a traditional official designation used in referring to the state. In 1776, Pennsylvania's first state constitution referred to it as both Commonwealth and State, a pattern of usage that was perpetuated in the constitutions of 1790, 1838, 1874, and 1958.  [c] One of Pennsylvania's two intermediate appellate courts is called the Commonwealth Court.
The name Commonwealth of Virginia dates back to its independence from the Kingdom of Great Britain. Virginia's first constitution (adopted on June 29, 1776) directed that "Commissions and Grants shall run, In the Name of the commonwealth of Virginia, and bear test by the Governor with the Seal of the Commonwealth annexed." The Secretary of the Commonwealth still issues commissions in this manner.
Among other references, the constitution furthermore dictated that criminal indictments were to conclude "against the peace and dignity of the Commonwealth". Additionally, the official title of the elected local prosecutor in each of Virginia's political subdivisions is the Commonwealth's Attorney, as opposed to State's Attorney in other States or the more standard District Attorney.
In Virginia, the term state is sometimes used in an official manner, usually in a compound structure rather than as a standalone noun. This is evident in the names of the Virginia State Corporation Commission, the Virginia State Police, and the Virginia Polytechnic Institute and State University. The state university in Richmond is known as Virginia Commonwealth University; there is also a Virginia State University, located in Ettrick.
- cf. the 17th-century Commonwealth of England.
- Note that In California, Colorado, Illinois, Michigan, and New York, criminal charges are brought in the name of the People. In all the other states, they are brought in the name of the State. Regardless of state, federal criminal charges are always brought in the name of the United States of America.
- A detailed history describing the origins of Pennsylvania's government, including its designation as a commonwealth from colonial times, is available from the Secretary of the Commonwealth's office. 
- Third Constitution of Kentucky (1850), Article 2, Section 1 ff. Other portions of the same Constitution refer to the "State of Kentucky".
- "Constitution of the Commonwealth of Massachusetts". Preamble of the Constitution of the Commonwealth of Massachusetts. Massachusetts General Court. Retrieved 27 October 2016.,
- Constitution of Pennsylvania, Preamble,
- The Hornbook of Virginia History, 4th ed., page 88.
- Paul Reinsch. English Common Law in the Early American colonies. Ph.D. thesis. Un. of Wisconsin. 1898.
- William E. Nelson. The Common Law in Colonial America. Vol. I. Oxford University Press. 2008.
- "7 fam 1120 Acquisition of U.S. Nationality in U.S. Territories and Possessions" (PDF). U.S. Department of State Foreign Affairs Manual Volume 7- Consular Affairs. U.S. Department of State. January 3, 2013. Retrieved December 13, 2015.
- See "Commonwealth", The Columbia Encyclopedia, Sixth Edition, 2001–07.
- The American Heritage Dictionary of the English Language, Fourth Edition, 2000.
- The Constitution of the State of Vermont, Chapter II, §§ 1, 8, and 71.
- Constitution of Delaware (1776), Art. 23.
- Warren, Joseph Parker (Oct 1905). "The Confederation and the Shays Rebellion". The American Historical Review. 11: 42–67. JSTOR 1832364.
- "CIS: State Symbols". 27 July 2004.
- PHMC: Pennsylvania History Archived April 3, 2006, at the Wayback Machine.
- "History of DOS" (PDF). Retrieved 2012-01-04.