This presentation provides a historical discussion of peak envelope cooling load calculation methods from the 1800s until the present. The discussion focuses primarily on U.S. analysis methods, and includes a discussion of the engineering-based methods that can be traced, either directly or indirectly to textbooks in the 1800s by Professor Eugene Peclet, at the College of Marseille in France, and Professor Hermann Rietschel, Professor of the Technical University of Berlin, Charlottenburg Germany.