Source: Historical Statistics of the United States 1789-1945 (Bureau of the Census, Washington, D.C., 1949), p. 46.

Sources:

James Bordley III and A. McGehee Harvey, Two Centuries of American Medicine, 1776-1976 (Philadelphia: W. B. Saunders, 1976);

Nan Richardson, Catherine Chermayeff, and Thomas K. Walker, eds., Medicine's Great Journey. One Hundred Years of Healing (Boston: Little, Brown, 1992);

Paul Starr, The Social Transformation of American Medicine (New York: Basic Books, 1982);

Francis Wilie, M.I. T. in Perspective: A Pictorial History of the Massachusetts Institute of Technology (Boston: Little, Brown, 1975).