What are the conditions required for a territory to become part of United States?

Question

This question is very related to Commonwealth United States Insular Areas, where I asked in detail about the Puerto Rico (and other areas) situation.

Now I am interested to know which are the legal requirements set in the U.S. Constitution, needed by a territory to become part of the United States with all the rights as any other State of the Union.

Let's say that tomorrow a territory in this planet want to form part of United States, the people in referendum approved that and that is their wish, so which are the steps needed, Where Do they knock the Door? in other words Which steps must that territory follow?

Answer 1

Quoting the Constitution:

Article IV - The States 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.

Clause 2:

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.

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.

1. The proposed state votes on the matter.
2. The proposed state officially petitions Congress for Statehood.
3. The proposed state must make sure it is following the constitution for its government.
4. Both the Senate and the House vote with a majority to accept the state.
5. 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.

Answer 2

The population minimum given in the Northwest Ordinance is 60,000. Some of the requirements on states in the past have included sorting out violent conflicts (Kansas) and making sure they didn't actually belong to another country (Texas).

Apart from that, Congress has to approve the state constitution, which has led to some controversy. Utah and New Mexico both had to work out some details. But that's about it. Congress has never refused a sincere request for statehood yet. Puerto Rico made such a request this year, so we'll see what happens.