Quoting the Constitution:
Article IV - The States Section 3
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.
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
Bottom line is, Congress gets to decide, so long as they aren't taking land from another state. So, how does the process typically work? Note, some of this comes from this source.
- The proposed state votes on the matter.
- The proposed state officially petitions Congress for Statehood.
- The proposed state must make sure it is following the constitution for its government.
- Both the Senate and the House vote with a majority to accept the state.
- The president signs the bill.
Now, what does Congress typically impose?
- Some population minimum
- Speaking English has sometimes been a requirement, to an extent. (Source)
- Prior to slavery being abolished, there were requirements to balance the number of slave vs free states.