States and Their Admission to the Union

The thirteen original colonies in North America could officially be admitted to the United States after the U.S. Constitution was written and signed by the delegates to the Constitutional Convention, on Sep. 17, 1787. Article IV, Section 3 of that document reads:

"New States may be admitted by the Congress into this Union; but no new States shall be formed or erected within the Jurisdiction of any other State; nor any State be formed by the Junction of two or more States, or Parts of States, without the Consent of the Legislatures of the States concerned as well as of the Congress."

The main part of this article grants the U.S. Congress the right to admit new states. The process usually involves Congress passing an enabling act that authorizes a territory to convene a constitutional convention, draft a constitution, and formally apply for admission. Then, assuming they meet any conditions set forward in the enabling act, Congress accepts or denies their new status. 

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The Original 13 U.S. States

By Robert Longley

Between Dec. 7, 1787, and May 29, 1790, each of the colonies became states. Since that time, 37 additional states have been added. Not all states were territories before they became states, however. Three of the new states were independent sovereign states at the time they were admitted (Vermont, Texas, and California), and three were carved out of existing states (Kentucky, part of Virginia; Maine part of Massachusetts; West Virginia out of Virginia). Hawaii was a sovereign state between 1894 and 1898 before it became a territory. 

Five states were added during the 20th century. The last states to be added to the US were Alaska and Hawaii in 1959. The following table lists each state with the date it entered the union, and its status before they were states.

States and Their Dates of Admission to the Union

U.S. Territories

There are currently 16 territories owned by the United States, mostly islands in the Pacific ocean or Caribbean Sea, most of which are uninhabited and administered as wildlife refuges by the US Fish and Wildlife Services or as military outposts. United States territories with inhabitants include American Samoa (established 1900), Guam (1898), the 24 Northern Marianas islands (today a commonwealth, established 1944), Puerto Rico (a commonwealth, 1917), U.S. Virgin Islands (1917), and Wake Island (1899).

Sources and Further Reading

• Biber, Eric, and Thomas B. Colby. "The Admissions Clause." National Constitution Center.
• Immerwahr, Daniel. "How to Hide an Empire: A History of the Greater United States." New York: Farrar, Straus and Giroux, 2019. 
• Lawson, Gary, and Guy Seidman. "The Constitution of Empire: Territorial Expansion and American Legal History." New Haven: Yale University Press, 2004. 
• Mack, Doug. "The Not-Quite States of America: Dispatches from the Territories and Other Far-Flung Outposts of the USA." W. W. Norton, 2017.
• "The last time Congress created a new state." Constitution Daily. The National Constitution Center, March 12, 2019.