Chapter XXX: Section III

I. 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.

II. The congress shall have power to dispose of and make all needful
rules and regulations respecting the territory, or other property,
belonging to the United States; and nothing in this constitution shall
be so construed as to prejudice any claims of the United States or of
any particular state.