Admission to the Union

Article IV, Section 3, Clause 1:

New States may be admitted by the Congress into this Union; but no new State 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.[4]

Shortly after the new Constitution went into effect Congress admitted Vermont and Kentucky on equal terms with the existing 13 states and thereafter formalized the condition in its acts of admission for subsequent states. Thus the Congress, utilizing the discretion allowed by the framers, adopted a policy of equal status for all newly admitted states.[3] The constitutional principle derived from these actions is known as the equal footing doctrine. With the growth of states' rights advocacy during the antebellum period, the Supreme Court asserted, in Lessee of Pollard v. Hagan (1845), that the Constitution mandated admission of new states on the basis of equality.[2]

This 2022 Congressional Research Service report examines the legal processes for admission to the Union

Historically, most new states formed by Congress have been established from an organized incorporated U.S. territory, created and governed by Congress in accord with its plenary power under Article IV, Section 3, Clause 2 of the Constitution.[14] In some cases, an entire territory became a state; in others some part of a territory became a state. In most cases, the organized government of a territory made known the sentiment of its population in favor of statehood, usually by referendum. Congress then empowered that government to organize a constitutional convention to write a state constitution. Upon acceptance of that constitution, by the people of the territory and then by Congress, Congress would adopt by simple majority vote a joint resolution granting statehood. Then the President of the United States would sign the resolution and issue a proclamation announcing that a new state had been added to the Union. While Congress, which has ultimate authority over the admission of new states, has usually followed this procedure, there have been occasions when it did not.[15][16][17]

Congress is under no obligation to admit states, even in those areas whose population expresses a desire for statehood. In one instance, Mormon pioneers in Salt Lake City sought to establish the state of Deseret in 1849. It existed for slightly over two years and was never approved by the Congress. In 1905, leaders of the Five Civilized Tribes (Cherokee, Chickasaw, Choctaw, Creek, and Seminole) in Indian Territory proposed to establish the state of Sequoyah as a means to retain control of their lands.[18] The proposed constitution ultimately failed in Congress. Instead, the Indian Territory was incorporated into the new state of Oklahoma in 1907.

Some U.S. territories existed only a short time before becoming states, while others remained territories for decades. The shortest-lived was Alabama Territory at 2 years, while New Mexico and Hawaii territories both were in existence for more than 50 years. The entry of several states into the Union has been delayed by complicating factors. Among them, Michigan Territory, which petitioned Congress for statehood in 1835, was not admitted to the Union until 1837, because of a boundary dispute with the adjacent state of Ohio. The independent Republic of Texas requested annexation to the United States in 1837, but fears about potential conflict with Mexico delayed the admission of Texas for nine years.[19] Also, statehood for Kansas Territory was held up for several years (1854–1861) because of a series of internal violent conflicts involving anti-slavery and pro-slavery factions.

Once established, most state borders have, with few exceptions, been generally stable. Notable exceptions include: the various portions (the Western land claims) of several original states ceded over a period of several years to the federal government, which in turn became the Northwest Territory, Southwest Territory, and Mississippi Territory; the 1791 cession by Maryland and Virginia of land to create the District of Columbia (Virginia's portion was returned in 1847); and the creation, on at least three occasions, of a new state (Kentucky, Maine and West Virginia) from a region of an existing state (Vermont was created from what was disputedly claimed to be a part of New York and was not admitted until New York consented); two large additions to Nevada, which became a state in 1864, were made in 1866 and 1867. There have been numerous minor adjustments to state boundaries over the years as a result of improved surveys, resolution of ambiguous or disputed boundary definitions, or minor mutually agreed boundary adjustments for administrative convenience or other purposes.[20] One notable example is the case New Jersey v. New York, in which New Jersey won roughly 90% of Ellis Island from New York in 1998.[21]

States that were never part of an organized U.S. territory.

In addition to the original 13, six subsequent states were never part of an organized incorporated U.S. territory:

• Vermont, admitted March 4, 1791, was formed from the territory of the Vermont Republic (earlier known as the New Hampshire Grants). This territory was also claimed by New York. The resulting dispute led to the rise of the Green Mountain Boys and the later establishment of the Vermont Republic. New Hampshire's claim upon the land was extinguished in 1764 by royal order of George III, and on March 6, 1790, the state of New York ceded its claim to Vermont for 30,000 Spanish dollars.[22]
• Kentucky, admitted June 1, 1792, was set off from Virginia (previously its western District of Kentucky counties). The Virginia General Assembly adopted legislation on December 18, 1789, separating its "District of Kentucky" from the rest of the state and approving its statehood.[23][24]
• Maine, admitted March 15, 1820, was set off from Massachusetts (previously the District of Maine, its northern exclave). The Massachusetts General Court passed enabling legislation on June 19, 1819, consenting to the separation of the District of Maine from the rest of the state (an action approved by the voters in Maine on July 19, 1819); then, on February 25, 1820, passed a follow-up measure officially accepting the fact of Maine's imminent statehood.[23] The act of Congress establishing Maine as the 23rd state was part of the Missouri Compromise of 1820.[25]
• Texas, admitted December 29, 1845, was formed from the territory of the Republic of Texas following the republic's annexation into the United States earlier in 1845.[26]
• California, admitted September 9, 1850, was formed from unorganized territory ceded to the United States by Mexico in the 1848 Treaty of Guadalupe Hidalgo at the end of the Mexican–American War. The Act of Congress establishing California as the 31st state was part of the Compromise of 1850.[27]
• West Virginia, admitted June 20, 1863, during the Civil War, was set off from Virginia (previously its northwestern trans-Allegheny region). The General Assembly of the Restored Government of Virginia passed an act on May 13, 1862, granting permission for the creation of West Virginia.[28][29] Later, by its ruling in Virginia v. West Virginia (1871), the Supreme Court implicitly affirmed that the breakaway Virginia counties did have the proper consents required to become a separate state.[30]

• 51st state
• An Act for the Admission of the State of California
• Enabling Act of 1802, authorizing residents of the eastern portion of the Northwest Territory to form the state of Ohio
• Legal status of Texas
• Enabling Act of 1889, authorizing residents of Dakota, Montana, and Washington territories to form state governments (Dakota to be divided into two states) and to gain admission to the Union
• Enabling Act of 1906 authorizing residents of Oklahoma, Indian, New Mexico, and Arizona territories to form state governments (Indian and Oklahoma territories to be combined into one state) and to gain admission to the Union
• Alaska Statehood Act, admitting Alaska as a state in the Union as of January 3, 1959
• Hawaii Admission Act, admitting Hawaii as a state in the Union as of August 21, 1959
• Federalism in the United States
• List of U.S. states by date of admission to the Union
• List of U.S. state partition proposals
• Perpetual Union
• State cessions
• Statehood movement in the District of Columbia
• Statehood movement in Puerto Rico

• The Uniting States: The Story of Statehood for the Fifty United States, three volumes, edited by Benjamin F. Shearer, Greenwood Press, Westport, Connecticut, 2004, ISBN 0-313-32703-3