Article 4, Section 2, Clause 1

Document 3

Vermont Constitution of 1777, CH. 1, ART. 17

XVII. That all people have a natural and inherent right to emigrate from one State to another, that will receive them; or to form a new State in vacant countries, or in such countries as they can purchase, whenever they think that thereby they can promote their own happiness.

The Founders' Constitution
Volume 4, Article 4, Section 2, Clause 1, Document 3
http://press-pubs.uchicago.edu/founders/documents/a4_2_1s3.html
The University of Chicago Press

Thorpe, Francis Newton, ed. The Federal and State Constitutions, Colonial Charters, and Other Organic Laws of the States, Territories, and Colonies Now or Heretofore Forming the United States of America. 7 vols. Washington, D.C.: Government Printing Office, 1909.