ly refers to all of these subnational jurisdictions as "States" (Article One, Section 2, Clause 1 of the Constitution, concerning the U.S. House of Representatives, in which Representatives are to be elected by the people of the "States"; Article One, Section 3, Clause 1, concerning the U.S. Senate, allocates to each "State" two Senators). For all of these purposes, each of the four above-mentioned "Commonwealths" counts as a State.
Since the establishment of the United States in 1776, the number of states has expanded from the original 13 to 50. The U.S. Constitution is rather laconic on the process by which new states could be added, noting only that "New States may be admitted by the Congress into this Union" and forbidding a new state to be created out of the territory of an existing state, or the merging of two or more states into one, without the consent of both Congress and all the state legislatures involved.
In practice, most of the states admitted to the union after the original 13 have been formed from Territories of the United States (that is, land under the sovereignty of the federal government but not part of any state) that were organized (given a measure of self-rule by the Congress subject to the Congress’ plenary powers under the territorial clause of Article IV, sec. 3, of the U.S. Constitution).15
Generally speaking, the organized government of a territory made known the sentiment of its population in favor of statehood, usually by referendums. Congress then directed that government to organize a constitutional convention to write a state constitution. Upon acceptance of that Constitution, Congress has always admitted that territory as a state. The broad outlines in this process were established by the Northwest Ordinance (1787), which predated the ratification of the Constitution.
However, Congress has ultimate authority over the admission of new states, and is not bound to follow this procedure. A few U.S. states (outside of the original 13) that were never organized territories of the federal government have been admitted:
- Vermont, an unrecognized but de facto independent republic until its admission in 179116
- Kentucky, a part of Virginia until its admission in 179216
- Maine, a part of Massachusetts until its admission in 182016 following the Missouri Compromise
- Texas, a recognized independent republic until its admission in 184516
- California, created as a state (as part of the Compromise of 1850) out of the unorganized territory of the Mexican Cession in 1850 without ever having been a separate organized territory itself16
- West Virginia: During the Civil War Virginia had two state governments, a Unionist one and a Confederate one, both claiming to be the legitimate state government of Virginia. West Virginia was created in 1863 by the Unionist state government from areas of western Virginia, after the Confederate state government's 1861 secession of Virginia to the Confederate States of America.
Congress is also under no obligation to admit states even in those areas whose population expresses a desire for statehood. For instance, the 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.17
Once established, most state borders have been generally stable, with exceptions including the formation of the Northwest Territory in 1787 and the Southwest Territory in 1790 from various portions of the original states, the cession by Maryland and Virginia of land to create the District of Columbia in 1791 (Virginia's portion was returned in 1847), and the creation of states from other states, including the creation of Kentucky and West Virginia from Virginia, and Maine from Massachusetts. However, there have been numerous minor adjustments to state boundaries over the years due to improved surveys, resolution of ambiguous or disputed boundary definitions, or minor mutually agreed boundary adjustments for administrative convenience or other purposes.16 One notable example is the case New Jers