Article 1, Section 9, Clause 8

No Title of Nobility shall be granted by the United States: And no Person holding any Office of Profit or Trust under them, shall, without the Consent of the Congress, accept of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince or foreign State.

1.William Blackstone, Commentaries 1:153--54, 261--62, 1765
2.Thomas Paine, Reflections on Titles, May 1775
3.Virginia Declaration of Rights, sec. 4, 12 June 1776
4.Benjamin Franklin to Sarah Bache, 26 Jan. 1784
5.Thomas Jefferson to George Washington, 16 Apr. 1784
6.Records of the Federal Convention
7.Cato, no. 2, 10 Dec. 1787
8.James Madison to Thomas Jefferson, 9 May 1789
9.James Madison, Title for the President, House of Representatives, 11 May 1789
10.Thomas Jefferson to William Temple Franklin, 20 Apr. 1790
11.William Temple Franklin to Thomas Jefferson, 27 Apr. 1790
12.St. George Tucker, Blackstone's Commentaries 1:App. 216--22, 295--96, 1803
13.Thomas Jefferson to John Adams, 28 Oct. 1813
14.William Rawle, A View of the Constitution of the United States 119--20 1829 (2d ed.)
15.Joseph Story, Commentaries on the Constitution 3:§§ 1345--46, 1833