<P> 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 separate 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 . 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 . 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 . </P> <P> In addition to the original 13, six subsequent states were never part of an organized incorporated U.S. territory . Kentucky, Maine, and West Virginia were each set off from already existing states . Texas and Vermont both entered the Union after having been sovereign states (only de facto sovereignty in Vermont's case, as the region was claimed by New York). California was set off from unorganized land ceded to the United States by Mexico in 1848 at the end of the Mexican--American War . </P> <Table> <Tr> <Th> State </Th> <Th> Date of admission </Th> <Th> Formed from </Th> </Tr> <Tr> <Td> California </Td> <Td> 000000001850 - 09 - 09 - 0000 September 9, 1850 </Td> <Td> Unorganized territory (part) </Td> </Tr> <Tr> <Td> Kentucky </Td> <Td> 000000001792 - 06 - 01 - 0000 June 1, 1792 </Td> <Td> Virginia (District of Kentucky: Fayette, Jefferson, and Lincoln counties) </Td> </Tr> <Tr> <Td> Maine </Td> <Td> 000000001820 - 03 - 15 - 0000 March 15, 1820 </Td> <Td> Massachusetts (District of Maine) </Td> </Tr> <Tr> <Td> Texas </Td> <Td> 000000001845 - 12 - 29 - 0000 December 29, 1845 </Td> <Td> Texas! Republic of Texas </Td> </Tr> <Tr> <Td> Vermont </Td> <Td> 000000001791 - 03 - 04 - 0000 March 4, 1791 </Td> <Td> Vermont Republic (earlier known as the New Hampshire Grants) </Td> </Tr> <Tr> <Td> West Virginia </Td> <Td> 000000001863 - 06 - 20 - 0000 June 20, 1863 </Td> <Td> Virginia (Trans - Allegheny region counties) </Td> </Tr> </Table> <Tr> <Th> State </Th> <Th> Date of admission </Th> <Th> Formed from </Th> </Tr>

New states may be admitted by the congress into this union