Article 4, 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.

1.Continental Congress, Oct. 1780
2.Articles of Confederation, art. 11, 1 Mar. 1781
3.Thomas Jefferson, Revised Report, Plan for Government of the Western Territory, 22 Mar. 1784
4.Records of the Federal Convention
5.Charles Pinckney, Observations on the Plan of Government, 1787
6.Luther Martin, Genuine Information, 1788
7.James Madison, Federalist, no. 43, 290--91, 23 Jan. 1788
8.Thomas Jefferson, Proposed Amendment to the Constitution, July 1803
9.Thomas Jefferson to William Dunbar, 17 July 1803
10.Thomas Jefferson to Wilson Cary Nicholas, 7 Sept. 1803
11.Rufus King to Timothy Pickering, 4 Nov. 1803
12.Gouverneur Morris to Henry W. Livingston, 4 Dec. 1803
13.Thomas Jefferson to James Madison, 14 July 1804
14.John Adams to Josiah Quincy, 9 Feb. 1811
15.Robert W. Reid, Admission of Missouri, House of Representatives, 1 Feb. 1820
16.Joseph Story, Commentaries on the Constitution 3:§§ 1309--15, 1833