I think our governments will remain virtuous for many centuries; as long as they are chiefly agricultural; and this will be as long as there shall be vacant lands in any part of America. When they get piled upon one another in large cities, as in Europe, they will become corrupt as in Europe.

Jefferson, Thomas. "Col. Smith, Nov. 13, 1787." The Life and Selected Writings of Thomas Jefferson: Including the Autobiography, The Declaration of Independence & His Public and Private Letters, edited by Adrienne Koch and William Peden. Modern Library, 1998.

Madison, James. "No. 10: An extensive republic a remedy for mischiefs of faction.--Madison." The Federalist: A Commentary on the Constitution of the United States, edited by Robert Scigliano. The Modern Library, 2001.

Pyrrhus. Quoted in "Pyrrhus." Parallel Lives by Plutarch. Oxford University Press, 2009, ch. 21, sect. 9.