Local governments can vote as much as they want it'll never happen. If I remember correctly it is in the constitution that you can't split up a state after it's been created.
Article IV, 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.
Basically, the parent state and Congress must approve.